Sure thing c: I'll try and be as thorough as possible here, but do note that some bits are speculation on my part, so take it with a grain of salt. Also, it goes without saying, but this analysis contains SPOILERS for the story this song is made for.

This song was written for the anime Domestic na Kanojo based on the manga by Sasuga Kei. More specifically, the song looks at the emotions felt by one of the characters in the story, Hina. She is a high school teacher who's mother just remarried, and one of her students, Natsuo, has now become her step-brother. The issue is, this step-brother has been in love with her since before their parents remarriage, and now the two of them live under one roof.

The first line "Inexperienced, heartless (uncertain), but even so, be beautiful.", refers to herself. She's still inexperienced in proper love (see later paragraph), is heartless because of how she responds to Natsuo's feelings for her, and uncertain because she herself doesn't know what she wants. The "be beautiful" is a message to herself: 'despite how much of a wreck I am, I need to keep up appearances as a teacher, as a sister, and as a woman.'

The line "No Destiny would tie you and me.", is a little bit of stretch on my part, but you can translate the line literally as "No Destiny, unsuitable". What she is saying here, is that there isn't a future between her and Natsuo. They are siblings now, she doesn't see a way to justify being in a relationship with her brother. The line "This alone won't be enough.", is her telling herself that just turning him down once won't be enough, Natsuo won't just stop loving her because she asked him nicely. The line "If I explain that properly, it should all work out.", is pretty self-explanatory; if she explains the situation their in to him, he should give up. The line "Things, Money, Love, Words, I'm tired of putting myself out there." has less tie-in to the story, and is more a general statement. But the line can also be interpreted as 'she's sick of being in the spotlight'. Just speculation here, but this line may refer to how Natsuo and her little sister Rui try to stop her affair, and how it feels like her life is now unwillingly in the spotlight.

Hina is having an affair with a married man in the beginning of the story. He used to be her first crush back in high school when he was her teacher, but she eventually started going out with him years later. He is in a loveless marriage and constantly tells Hina that he will divorce his wife soon. "Déjà vu", refers to how similar Natsuo's current situation is to her past self. "What are you so unsatisfied with?", is her asking herself: 'does being desired by someone really feel all that bad? Isn't this what you wanted?'. She wanted to be loved, but instead of by the man she's seeing, she's being loved by her step-brother. The following two lines also tie-in to this idea. Her wanting to date a married man is a selfish act on her part, and is straining her relationship with Rui and Natsuo. She shouldn't be asking for more than what she has already, she should cherish her family instead of chasing after this man. So she ends her relationship with him.

The line "Just stop, "I'm sick of hearing those lines."," is probably referring to two lines in particular. The first being from the man she's seeing: "I'll divorce my wife soon, I promise". The second being Natsuo's confessions of love. For the line "Leaving things unfinished is the one thing I hate.", I tried smoothing out the meaning relative to the song. In relation to the story however, it means something slightly different. Instead of hating things that are unfinished, it's hating things that are half-assed. As in, she doesn't want to be stuck in a half-assed relationship with a married man, nor does she want a half-assed secret relationship with her step-brother.

In the chorus, the 'why' in line "Even if you say you 'love me', or ask me 'why'?", is referring to the question of "why can't we be together?", that Natsuo has likely asked her. The line "It's easy if it's just for fun, but doing this for real is too absurd.", refers to the time where Natsuo first confesses to her, and she humors him by making out with him. She goes as far to push him on her bed before she see's him being afraid of her. If her brother just wanted her body, she'd just do it with him and get it over with, but the fact that he wants a proper relationship makes the whole thing impossible and completely absurd. The line "Those thoughtless words, those flimsy (weighty) words.", refers to words like "I'll always love you.". To her, his words seem flimsy, there isn't any weight behind them. The issue is that if he really does mean what he's saying to her, she can't take it lightly. The line "Even if I got my hopes up for this fixed game,", can refer to the man she is seeing, or Natsuo. The 'fixed game' is the fact that she'll lose out to someone else, the man might choose his wife over her, and Natsuo might fall in love with someone younger and better for him. The next line, "Words that get my hopes up, let's make it all taboo.", is still talking about the man and Natsuo. They both give flimsy promises that she can't trust, so she wants them to just stop, make saying those words taboo. The final line in the chorus is very important to the overall progression through the song. First, "Take a hint" is probably the part of the translation I'm least confident in because there is a slight connotation from the verb tense in the japanese that makes it hard to translate. It technically is "I took a hint" or "You took a hint". In this chorus, the line means "I took the hint, I understand the situation we're in right now". The "please don't let it rain." part introduces Natsuo's love for her as a metaphor, rain. It is relentless and constantly showering her. At this point, she wants nothing more than for this rain to stop.

The next major line that I haven't covered in a previous comment is "I spread this fragile fan, because you find it more attractive that way, don't you?". It refers to her attempt at acting weaker and more helpless than she actually is. Why? Because the main character is the type of person who will help anyone in need, regardless of who it is. It's her attempt at getting his attention. At this point in the story, Hina and Natsuo begin a secret relationship as lovers.

Now onto the second chorus. "Confused." is talking about her feelings, she doesn't know if she wants to push him away or keep him close. The lines "If you can't answer, please leave me alone." and "If you can't stop hesitating, please leave me.", are her main worries as they're dating. How are we going to tell mom and dad? Are we going to get married? What future do we have together? Natsuo is hesitant because he doesn't have a solid answer for any of those questions. He wants to continue with their loving relationship in ignorance, he doesn't want to think about 'tomorrow', and wants to enjoy the 'present' where they're together. The line "The crucial words go in on ear, out the other. Just let it bring you peace of mind." follows that same train of thought. He ignores the most important issues and just wants to continue enjoying the bliss that is them being together. We then reach another rain metaphor, "If this sweet rain fell on you, It'd make you want to hold up your umbrella wouldn't it?". Natsuo's love for her is sweet and pure, so much so that she feels guilty almost. She feels like she can't let him love her this much, it's pouring with no sign of stopping even when their relationship is getting dangerous. That is when they are caught by the school. In a photo on a school trip, there is photographic evidence of Hina and Natsuo making out. An illicit relationship between teacher and student. Hina begs the school to let Natsuo get off scot-free while she moves to a remote city to teach there instead as her punishment. This is where the tone of the song takes a change. "I'm glad I kept my hopes up", she's glad she loved him. "I closed my eyes", she ignored her surroundings and loving him without worrying about their relationship. She "wanted to change" from the cold person she was before and wanted to reciprocate his feelings for her. This whole time she feels like she was only "pretending to be an adult.". After all that, their relationship is now "Lost. Irreparable.". Now she understands her feelings for him and pleads, "please don't stop raining.". She needs to see him again, before it stops raining, before he doesn't love her anymore and moves on.

The next two lines are a bit too vague for me to guess tbh. But the line after is one of my favorite in the whole song, "So please,I don't care anymore, it hurts right here (I want to stay here).". She acknowledges her feelings, she's know what she's done has hurt him, she knows that their relationship won't be the same, but she still wants to be with him. In the MV, when she says the line "it hurts right here", she clenches her chest. Her heart aches. Not only that, but the phrase can be interpreted as a simplified version of "I want to stay here", aka she wants to still be with him, be part of his life.

The final chorus has the line "Those thoughtless words, those weighty lies (truths)," that mirrors the first chorus but also eludes to another plot point that has happened while she was away from Natsuo. Her little sister Rui confessed to Natsuo and they are now dating. He's moved on, and with her sister no less. This isn't a lie, it's a heavy heavy truth. Now the "fixed game" line from earlier bares it's fangs. He loves someone else now, it was all a fixed game that she had no chance of winning. She was destined to lose. Natsuo wouldn't end up with her. But instead of crumbling in the face of this truth, she decides to "put an end to this habit of running away." She decides that even if he won't chose her, she will continue to love him. She wants to be honest with her feelings now.

This leads into the final line, "It's raining again today. I'll close my umbrella, and go home in the rain.". Natsuo's feelings (the rain) continue, but whether it's for her anymore she doesn't know. She decides that she won't try and shield herself for the truth anymore. She'll go home, to his side, and be with him, even if that rain is for someone else now.

(sorry about any formatting issues in this post btw)