I agree with you. Take and Mine have an aggressive love-hate relationship that is actually more balanced and honest exactly because there is no manipulation between them and they both have equal power to hit back.
Hiroi is a selfish child. The relationship is to his taste and rule. He uses the feelings of both men towards him ( Mine is in love with him and Take friendship) to create a relationship that he wants.
I think the author wanted so bad to create an edgy threesome relationship and that's why Hiroi is there just to complete the triangle but the dynamic and chemistry is totally damped down by Hiroi. He is unremarkable, he seems mildly mentally challenged like a child who didn't grow up. Take seems more like his big brother that for some reason can't let him fend for himself and honestly, the explanation on why Mine falls in love with him seems more like lack of self esteem and clinging to the first person who was nice to him. Never mind that Hiroi is not even a convincing seme. Its just weird that he dominates both men. Take and Mine seem more like the parents of a slow witted child.
Take x Mine will always deserve a story of their own.
i made my account just to comment on this yaoi. now i first found this manga really early on into my yaoi exploration back when i was about 10-12 years old. at first i didn't like it at all. i was pretty against the whole poly/threesome relationship. however, i grew to really love this story. just to be clear before i explain some things, i am fully on board with Take x Mine without Hiroi in the picture. this relationship is toxic, no doubt. personally, i believe that the toxicity comes from Hiroi alone.
[spoiler warning]
you can see it first in the scene where he tries to force double penetration on Mine when Mine was clearly scared and did not give consent. Mine is crying his eyes out and yet apologizes to Hiroi for hitting him when Hiroi absolutely deserved to be hit. Hiroi does not for a second deserve that apology. the second time we see Hiroi being toxic are the past relationships/memories with Hiroi giving all his random stuff to Take. Hiroi is practically devoid of natural reasoning since he doesn't understand why other people don't want both him and Take. when he sees Take and Mine getting along, especially in sex, he just then starts to feel jealousy. he puts a limit on Take and Mine having sex alone for up to 3 times (which goes totally against his entire sharing shtick), he doesn't discuss anything with Take or Mine beforehand, and visibly gets upset that Take and Mine kiss. lastly, i feel that Hiroi is a barrier between Take and Mine's relationship. although Take and Mine didn't get along at first (and sometimes still don't), that dislike between the two was because of Hiroi anyway. to stay together with him, Hiroi basically forced Mine to have sex with Take. that's a low blow since i'm fairly certain that Hiroi didn't tell Mine beforehand about the whole 'share with Take' deal. you can tell that Take and Mine are growing close to one another and like eachother, or at least they would have an real love relationship if Hiroi wasn't in the picture. since this manga doesn't seem to have any other chapters happening anytime soon, i like to believe that the 3 of them would still be together, but Hiroi wasn't able to stop Take and Mine from growing super close, close enough to call it love.
anyway those are my thoughts. Take x Mine is otp.