
Spoilers:
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It turns out from a young age, the seme enjoyed seeing the uke all vulnerable and made him reliant on him (dressing him, homework, etc). He ends up dating the new guy (Mizuse) to make the uke go crazy with jealousy. Once the seme makes the uke desperately declare he is the seme's, he immediately ends it with Mizuse. And it turns out Mizuse knew all along and just played along (asking seme out) to get some D. By the end uke realizes that being dominated by the seme is the best.

Thanks for the spoilers @Anon. Now I know not to waste my time reading this manga.

Basically it's ntr.

Mizuse just wanted a friend with benefits. He knew from the start that Kei was obsessed with his childhood friend. And even when Mizuse was shot down, he offered to help Kei make sure that Naru would be Kei's (creating the elaborate scheme of dating etc).

Lol np.

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Wait, so the seme despite being obsessed with uke still sleeps with glasses dude? Ugh I know uke did that but it feels so wrong

I actually didn't consider that at first but you're right. Still this section is gonna erupt with rage when that part is translated.

If you wanna talk about fairness, i personally don't think is fair. The uke was acting as a seme when he penetrated the glasses dude...in other words, his asshole wasn't used by anyone else...only the seme had used his asshole....the uke was a uke solely for the seme.
The seme on the other hand uses the same penis he used to penetrate his beloved uke to penetrate another guy (i.e. the glasses guy)...in other words, the seme is not a seme solely for the uke.....he is a seme for other guys too.
But leaving this issue of fairness aside, i don't like how the seme is thinking....there are so many ways to get the uke to realise and confess his love for you....he didn't need to resort to having a "couple act" with another guy to get the uke to be jealous! The seme had even gone to have sex for real with the glasses guy to make the "couple act" a real deal....If i am the uke, having a twisted mindset like the uke, i would have just forsake the seme and look for other toys to play with.

Sex is sex. He still slept with him and opened that door (3rd party) to their "relationship."
Read the raws, i think both the seme n uke have twisted mindset. This manga is officially out of my reading list.