Part 2 of my Ted Talk.
You're saying this like it's some sort of revelation. But we already knew since long ago, 13.5 has her lamenting the fate that it just had to be Yuu who Hikari fell in love with.
I mention it more to point out the contradictions existing in Yami. She previously went on and on about supporting Hikari's love and talking about how Hikari is going to confess to Yuu and that it will go well. I also point this out because I'm setting things up for when I talk about Yami's sabotage.
That's only natural, they haven't seen each other for a year and it's an absolutely dramatic and thrilling moment for her, yet his first words are about Hikari not being there. She is frustrated by the discrepancy between her own emotions and his attitude.
Again, I'm using this as evidence of her contradiction between wanting to support Hikari but also wanting Yuu and using it as evidence that Yami is going to consciously sabotage. She spent time in Chapter 39 talking about supporting Hikari but then instantly gets angry when Yuu mentions Hikari before even talking to her. I'm right there with you in agreeing that she's "frustrated by the discrepancy between her own emotions and his attitude." While she wants to be supportive of Hikari (or at least she thinks she wants to be), Yuu focusing on Hikari first instead of Yami is another straw being placed on the camel's back that's going to lead to Yami self destructing.
Where? She brings her up herself.
So after their initial confrontation, Yami herself brings up Hikari (after being mad at Yuu for mentioning her). Yuu shuts down this line of questioning and Yami gets mad when Yuu doesn't want to talk about Hikari. I'm bringing all this up to show the contradictions inside Yami's mind. Yami goes from pledging to support Hikari to getting mad that Yuu mentioned Hikari before her to then bringing up the topic of Hikari (which has already made her mad) and then getting mad when Yuu doesn't want to talk about Hikari.
Yuu talks about Hikari = Yami gets mad. Yuu doesn't talk about Hikari = Yami gets mad. Basically, I'm just trying to list instances where Yami appears to be all over the place in her thoughts.
I am completely missing the logic here. If what she's thinking and what she's saying are out of sync, why is your conclusion that her thoughts must be false? I can follow up on further points when you say her thoughts might not be real, but first explain the logic please.
So, I'm coming at this with the thought that Yami is an unreliable narrator. She's had several instances where she thinks A and then immediately says no I think B all while she's saying C. It becomes difficult to fully know whether A, B, C or some combination or maybe some unknown D is the truth. I believe Maruto is writing her this way on purpose.
That being said, I think Yami lies to herself in her thoughts. I think two opposite ideas about Yuu are existing in her head at the same time. On the one hand, she believes Yuu hasn't done anything wrong and it's all her fault that things turned out this way. At the same time, part of her is mad that Yuu never picked up any of her nuances, took things at face value and never fought for her when she ghosted him. She's also just pissed at the unfairness of her life - shitty step dad, mom who tried to kill herself and is now simultaneously dependent solely on Yami while also fighting with and hating/disliking her daughter, the thought that she doesn't deserve a man when she deprived her mother of hers, the fact that her best friend is in love with the guy she still loves, etc.
I think later on in Chapter 40 when she starts berating Yuu for not fighting for her - Yami is internally contradicting these statements but I believe there's truth in them and that deep down at least a part of Yami agrees with what she's saying. I think her guilt on what happened to her mother and her guilt for not telling Hikari about Yuu when she found out back in June is causing this split inside her. Yami feels like she's not deserving of love so she's trying to sacrifice herself and her love to help out Hikari but part of her is like "fuck this when do I get my happy ending?".
So, ultimately, I think Yami's internal thoughts are not the full truth but just one side of the coin.
Are you actually implying this is a manipulation? I mean, she is having an emotional outburst, pouring out her feelings on him all the while questioning her own words, and you think this is all intentional just to prevent him from going to Hikari? This is just too Hikari-centric if you ask me. Like, she is laying her feelings bare before the boy she loves, and you think there is actually some friend on her mind at that moment? Just ridiculous.
I think the entire time Yami is talking to Yuu in Chapter 40 she's fighting with two contradicting ideas in her head: 1) I need to suppress what I feel for Yuu and sacrifice my happiness so Hikari can be happy and 2) It's not fair that I don't get to be happy - I want to be happy - I want Yuu but I also don't want to lose Hikari.
She starts out by verbally saying things to drive Yuu away - how she's bored of him, how he's got a new girlfriend, how he needs to leave her and go to Hikari all while internally wondering how in the world that Yuu is taking her lies/manipulation at face value. I fully believe that at first she's manipulating Yuu to get him to leave her and go to Hikari. It goes on up until the internal monologue where Yami says:
He’s kind, sort of cute, a little too easy to sway…
But that time, I was the one who nudged him in that direction.
So I can’t. I can’t go any further than this.
I can’t tie him down.
Not to this place.
Not to me.
She's acknowledging that Yuu is easy to sway and that she's nudged him in a certain direction before. She's trying to do this again to get him to go to Hikari thereby fulfilling idea #1 mentioned above.
After that, Yuu hesitates and gives Yami a glimpse of the man she fell in love with.
Just for that one moment—he had the face of a real guy.
The face Yuu had when I was head over heels for him.
She tries to get him to hurry up and go because she doesn't want him to see her lingering feelings and then Yuu says "Okay then, Yami-senpai, see you--"
It's at this point I think idea #2 starts to take control of Yami. She starts thinking about how she's trying to get him to go and he's finally walking away and he's going to leave her forever and she can't handle it. Once again Yuu is walking away from her which is something that really bothers her. She's mentioned before that Yuu always lets go at the most important moments.
She could have stayed silent and let him walk out but instead she calls out to Yuu and says "“...What, are you trying to turn this into a memory or something, Yuu?”.
She even thinks to herself "What the hell am I saying?". She's contradicting everything she's done so far to push him towards Hikari and now it seems like she's trying to pull Yuu in. She starts talking to him, saying things she wished he did while thinking about how unfair she's being. She wants Yuu but she feels immense guilt because of Hikari so her thoughts, words and actions are all over the place.
My raised hand struck Yuu’s cheek with a dry smack.
He had come back—
Even though he had walked away, he was now right in front of me again.
Because he’d returned to be blamed, to be yelled at.
Now, instead of pushing him to go meet up with Hikari, she's talking to Yuu and getting him to engage with her again, keeping him with her. He's back in front of her. Her goal has now switched 180 degrees. With her words (whether they are lies, the truth or a combination) she has manipulated Yuu into not going to Hikari but instead coming back to her.
I believe it's at this point that Yami sees Hikari watching them through the doorway and it's at this point that Yami makes a decision to kiss Yuu. I'm not sure how to interpret this as anything other than both a self-destruction on Yami's part and an attempt to sabotage Hikari.
Yami's friendship with Hikari is very important to her yet she knowingly kisses her best friend's crush in front of her best friend. If that isn't a self-destruction I'm not sure what is.
Yami knows Hikari was planning to confess to Yuu. Seeing your best friend kiss your crush is almost certainly going to mess up your thoughts and feelings and interfere with your plan to confess. That sounds to me like sabotage and a conscious one at that.