Honestly it depends, considering author rolled back that teach with agawa thing. Personally think it’d be funny if her and inukai formed an actual relationship as they both know what its like to be cucked now and inukai has a thing for girls that reject him.
Irl I think an open relationship between Inukai and Agawa could maybe suceed seeing as they both have high sex drives and are equally able to get multiple partners (Agawa is a woman offering free sex and Inukai is stated to be notably attractive and has girls offering themselves up raw to him). Gotou said he learned his moves from Inukai which were working on Agawa so Inukai can definitely satisfy her in that department. Inukai is lacking in the emotional aspect though since Inukai can be very deranged when he is horny (trying to fuck Shiina while she is sleeping or making it his mission to cum in Agawa when she always stresses protection), assuming he did some reflection after getting cucked though, he should be more reasonable now.
Another thing Inukai lacks, especially compared to Gotou is stamina and while Inukai has experience with threesomes where he was able to satisfy both girls meaning he probably has relatively decent stamina, Gotou is too cracked in that department (cumming like 20 times or something in one session) so while he may be able to last longer than most, he won't last as long as Gotou. Regardless though, Inukai could probably just teach Agawa about threesomes if her stamina is that high. Then Gotou can just get with Akito since they have history together, she has a crush on him and they even have a mutual interest (beyond sex) in baseball assuming Gotou can get back into it.
You could potentially argue that Inukai may be the more possessive type and may not want a girl who sleeps around while he does all the sleeping but he literally has a crush on Shiina who is on the same level of promiscuity as Agawa so there is a chance he would be fine with it. The guy even had a super boner while he was being cucked so maybe he would be into it lol. For Agawa it also depends since she was bothered by the threesome with Shiina but she still went through with it in the end and I imagine she was mainly put off by the fact she's in a threesome with her biological (half) sister and especially that her sister kept stealing any guy she liked and was basically doing it in her face.
Of course, do I think nor want this to happen? Never, since it would be too boring compared to the trainwreck of Gotou who recently lost his virginity trying to get with Agawa the super slut and taking Ws and Ls along the way, however it was an interesting thought that came to my mind spurred on by
@G33kG0dT4und3r's comment.