don't skip on dialogues, and it's good to reread. also, there will be a flashback on the later chapter to explain things. they do not hate each other. they are somewhat a tension-filled rival and bestfriends. ran is just tsundere.
it doesn't have to be a sappy verbal agreement to see that they are together. they started as physical relationship but that's just an excuse for the both of them.
and again, for your third question. they are bestfriends/childhood friend. come college, they used an apartment that ranmaru's family own and lived there together. it will only be revealed in the later chapter so read the whole story first and let it flow. the answers are there.
if it helps, read my review above as i made little recaps on each volume.
I don't understand a thing about this manga, so please, help this stupid fujoshi here.
First chapter Kei and Ranmaru seems to dislike other and make out, okay. Then, in the second chapter they are all love-dovey thing without even talk about what happened between them. Confusing, but still okay.
Then, Kei is thinking about his family and a car hits Ranmaru. Okay, but Ranmaru and him were together? Kei left for work and Ranmaruu stay at home (probably his own, but that was not explained).
And Ranmaru was hugging him in the hospital, but they were close enough for Ranmaru to save Kei's life risking his own? Or this is something in a different timeline from the first chapter (past or future)?
I'm so excited about this manga because I never saw no one dislike, but it seems to confuse for me, so please help me!