a character is partly developed through their relationships with other characters. but i think that with Higashi it's even more evident how much his whole being depends on other people. at least writing-wise.
Hamura represents his loyalty to the yakuza (the institution, something bigger that decides what's right for everyone). to Hamura Higashi is just a tool to get what he wants, but Higashi depends on Hamura and he scarred him, he can never forget him. he (accidentally) got Higashi to witness a robbery in which he might have lost his life; got Kaito out of the family and Higashi even thought it was his own fault; when he found out the truth, Hamura threatened to kill Higashi and then forced him to KILL A MAN. we know through Tashiro in LJ that Higashi probably wasn't even great friends with other people in the family. he was hurt and couldn't tell anybody. it wasn't even Hamura's objective because Higashi wasn't even supposed to witness the robbery, nor the meeting in the sewers. maybe Higashi had this in mind and felt even guiltier, not really blaming Hamura (we don't know though).
Kaito represents his loyalty to his own values, ethics, and people he loves. in Kaito Files we see Higashi being 100% himself, and he's only that way with Kaito: sweet, and maybe even a little goofy. i love how sweet they are to each other, i think people mischaracterise them as Higashi being Kaito's lapdog, but it's a perfectly equal friendship, although Kaito uses to be his superior. yes, Higashi would give his life for Kaito, but Kaito would also give his life for Higashi, hell, he didn't fight the robber back and he almost lost a pinky just because he wanted to protect Higashi. in terms of character development and writing, Kaito's character also heavily depends on Higashi, not just the other way around. through Higashi we discover that Kaito has a life outside of Yagami and the detective agency, and he's not just the funny sidekick, he has very deep scars.
Higashi begins to change, or, well, he is forced to change when these two reference points come clashing. i think that even before being expelled, Kaito constituted a different "reference point" (not sure that makes sense, sorry) than the actual institution aka the yakuza. Kaito stood up for Higashi when his superiors would beat him up, even if idk if Kaito could actually do that, but the thing is, he did it anyway. Kaito was still under the yakuza in any case, so it aligned even with some discrepancies.
when Kaito gets out of the family, Higashi realises that his personal values, or his heart really, don't align with what he's being told. but Kaito is gone, Higashi needs to save his face, so he becomes the picture perfect yakuza… which doesn't work perfectly, partly because he's not perfect at it, and partly because of how people see him. to others, he will always be a scaredy cat, especially in Hamura's eyes after what happened in the sewers. Yagami tells him he's "finally looking like a real yakuza", but this just tells us that for how different Higashi can be, his past self cannot be deleted or forgotten and his reputation is just tied to that. in a way, it's not like much inside him changes, either. he just acts a bit more like a dick than usual.
finally, Yagami represents change. Higashi hates him for obvious reasons: he gets to bask in Matsugane's grace without actually being a yakuza and leads a rather successful life. as the localisation producer said, Yagami had a choice, while higashi was forced into the yakuza life. but later he sees that Yagami is worth the trouble. he doesn't want to admit to liking him, because that would mean admitting he was wrong in the past, i think he's that simple. and, well, it's just principle. it's as if Yagami took advantage of the family, although he didn't choose to be the favourite child lol. Higashi would never admit it, but he and Yagami can be alike. "devoted" to Kaito, fighting for what's right, and bearing a terrible past they want to forget. but it's when Higashi starts liking him and siding with him that he changes, he realises that change is hard and difficult, but he can go through the hardships if it's for a good cause. Yagami turned Higashi's life around, literally removed Hamura (and in a way also Matsugane) from his life.
that is not necessarily a good thing, because it caused great trouble inside the Matsugane family, and apparently it was mostly Higashi who had to deal with it, acting as the one in charge. about one year later, the yakuza also disbanded, and Higashi started to actually take care of Charles, becoming its actual manager. he's not being backed by the family, neither financially, nor bureaucratically, nor factually. imagine going through all that in the span of one year + what happened in the previous year as well with Kaito's expulsion, after years and years of living the same yakuza life. if you think about it that way, it makes sense that Higashi is still resentful towards Yagami. but it's a so much better life than he could have ever imagined.
and now he's opening a new Charles branch in Ijincho (although he canonically has very few customers…? somehow…?) and if they aren't doing this for a third Judgment game then idk why they wrote that. please give us Judgment 3. and make Higashi more important in the lore… he's kinda useless in Lost Judgment. he has SO much potential (i wouldn't have written this otherwise) and it's going to waste.
