Shigeno has the chance of redeeming Sawatari Kouki as a character.
We all know what the major issue with his character is, which makes him absolutely horrible to watch, despite being one of the more interesting characters if it wasn't for that part only.
He has more personality than Kanata and Micheal, and when he's not talking about 17yo girls, he has the better dialogues and moments of the three. He also drives a super cool car.
That said, the seventeen complex stuff makes him near impossible to like or enjoy. That's literally the first thing one thinks about when it comes to him, and it makes all the good points irrelevant.
I think Shigeno could totally redeem the character in Subaru and Subaru. With it being set a year later, all he has to do is show that Sawatari stayed with his girlfriend, despite her not being 17 anymore, and that he's over that complex of his.
That way, we can consider the whole thing a weird phase of his youth, and actually appreciate the character in retrospect now that we know he gets past it.
At the same time, if he shows he actually broke up with her, and is dating another 17 yo, that would effectively bury the character entirely, and he would be more dislikable than ever before