Shigechi: worked really well as a character that taught Gotou the meaningless of casual sex without feelings. No matter what some commenters think, I don't think Shigechi wanted Gotou and truly just had sex with him out of pity and maybe curiosity due to Agawa hyping up Gotou's sex skills. Even though she's fan favorite, Shigechi's arc with Gotou is over and I don't see her coming back.
Inukai: great villain turned bro/rival, as he forced Gotou to grow as a person by being more proactive and direct with his feelings. Plus, he's gained respect for Gotou as a person, esp after Gotou cucked him with Shiina (Inukai has so many women, he'll be fine lol).
Akito: feels like she's benched right now. I think her potential isn't completely used up yet, and that she might possibly be reused later on as a serious love interest once Gotou gets solidly rejected by Agawa down the line (he's never directly confessed to Agawa). Moreso than sex, I think Akito represents the wholesome side of love, and I sense Gotou will eventually have to directly reject a sweet girl like her to be true to himself and his love for Agawa. I see Akito as the main love "rival" to Agawa, and believe she will return stronger than ever as a main romantic interest someday.
Kiyomi (the teacher): I don't think she's a replacement for Akito in the "pure childhood friend" slot, as in this chapter, we see Gotou being a bit uncomfortable with her advances, esp after his epiphany about how meaningless shallow sex can be (thanks to Shigechi). I think she's a potential yandere who might seduce Gotou, who will eventually have to get his shit together and reject her (perhaps by being reminded of his deepest desires for Agawa by someone, hopefully Agawa). But of course, there's an overlap with Akito's childhood friend archetype, and tbh I'm pretty disappointed in her introduction to the story. Leans more towards fanservice than necessary plot development imo.
Gotou: poor guy getting tossed left and right cuz Takeda Super wants any excuse to add more fanservice favs (like milf/teacher/childhood friend right now). He's grown as a character, but as of right now, def at a low - Gotou will eventually need to grow a pair and directly confess to Agawa (who will either 1. reject him or 2. agree but the 1st relationship will fail).
Agawa (my queen): She's an interesting character who's charm lies in the fact that no matter how many people she sleeps with, deep down she's just a wholesome girl who's afraid of emotional intimacy. In the most recent chapters featuring her, we see how dissatisfied she becomes with sex with her sex friends, due to how Gotou's intense romantic feelings touched her. We see this part of her in the retconned timeline, as she blushes when Gotou chose her over Shiina and struggles to figure out what to do about this situation with Gotou. Sure, Agawa sleeps around and enjoys it, but I think it's mainly a coping mechanism to hide this fragile side of her, which prob originated from family issues (missing dad, being one-upped by Shiina, etc.).
I think Takeda Super is saving her character growth for the final arc of this series, where Agawa has to confront her fears of emotional intimacy directly and also return Gotou's feelings by confessing back to him (who still has a lot of work to do to earn Agawa's heart, thanks to Takeda Super dragging this series out lol).