I dont quite understand the whole story but i love it! If anyone would love to explain to ...

Okay, so...

Enishi's dad had an affair with Kuruto's dad, and Enishi's mom found out and left. Enishi's dad found out that he had a terminal illness and only had a short time left to live, so he got his affairs in order, but didn't know what to do about Enishi. So he went to his lover's house and asked him to grant him a final dying wish as a favor to his ex-lover, "if you still love me...", to take Enishi in when he passed away, in order to keep the child from being alone. So the "first time Kuruto wears funeral clothes" is when his father's lover (Enishi's dad) dies, and Kuruto meets Enishi while he's holding the book his father wrote for him before he died. They take Enishi in, but Enishi both looks like his father and reminds Kuruto's father of his ex-lover, so Enishi's adopted father always keeps busy and stays away from the house. The adoptive mother doesn't give two shits about the adoptive father because she knew about the affair, but wouldn't leave Kuruto to his father so she stayed to raise him, but she isn't all too fond of the idea that she has to raise her husband's ex-lover/affair's child as a promise of his love for him, so she keeps her distance from Enishi. But before all this happened, Yukito had a cat that he loved, and when Kuruto found out, Yukito was pissed but didn't want Kuruto to hurt it so he told him to protect it for him. Then... I don't know what happened but I think the cat got hit by a car or something, and Yukito had to bury it... and didn't want to see Kuruto cry, so he kept it from him, and made Aruma (youngest brother) swear never to tell Kuruto what happened. Then while Yukito was still upset and grieving, Kuruto got extra clingy since his brother was distancing himself more and more, and followed him up to the cliff when Yukito yanked his arm away, accidentally causing Kuruto to lose his balance and fall off the cliff. Then Kuruto became scared of his brother, so Yukito moved away to let his brother feel safe in his own home. But by not telling Kuruto what really happened with the cat, Kuruto either thinks he lost the cat and broke the promise to his brother so he feels good-for-nothing, or he thinks his brother killed it because Kuruto wasn't doing a good enough job.

Kuruto feels like his entire family is leaving him so he attaches himself to Enishi, they grow up together and fall in love with each other, but Kuruto is afraid to admit he loves Enishi because the last time he admitted he loved something (the cat, his brother) they were taken away from him. So he acts indifferently towards Enishi until he finally talks things out with his older brother and finds out the truth. Then he finally folds and admits he loves Enishi too, and they sleep together only to be caught the next morning by the youngest brother Aruma, WHO has been quite openly crushing/in love with Enishi as well but mostly just stayed in the background. (Poor thing.)

And that's where it ends... when he's finally able to receive Enishi's feelings and expressions of love towards him, while also being able to communicate them back mutually!

THE END!

-Shadow

Thanks to you I got it but I still have a question, where lives Aruma?

And yes Aruma is a poor thing.
There should be a manga about him and his love life.

I think you are right about everything apart from the cat part. Kuruto fell off the cliff before the cat disappeared since he was looking for her while wearing all those bandages, so my guess was that the cat hurt him and Yukito "got rid of it", maybe because I'm a weird person, but it can also be like you said, that it died and he buried it. But still, blood on his face and scratches? I don't think a dead cat can give you these except from when it's attacking you back... alive. Idfk, this part is confusing. But I got that he felt guilty about the whole pushing his brother off the cliff thing so he ended up trying to protect him in... alternative ways to say the least (no matter if he killed it or just plain buried it -alive?!?). My other guess is that throwing his brother off the cliff turned the yandere switch on and just went batshit crazy on the poor cat because he wanted to take his brother's liked things and people.
Either way i end up sounding crazy. How nice.

But whatever, point is Kuruto was scared shitless to have his brother find out the next thing he liked was Enichi. He probably thought he was gonna bury him too. OR it can be what you said. I think the translation also got things mixed up. A few things didn't make sense in an obvious mistranslation pattern.
Props to the middle brother who could take all that shit from his family without ditching them. That or he's the mastermind of it all. Plot twist!

I understood that Aruma was actually in love with Kuruto rather than Enishi. Because in Ch3 page 14 he asks Kuruto "why do you think I come walk you to school every morning?" And Kuruto says that is because of Enishi, and then Aruma says he understands nothing. So it gave me more the impression that Aruma was actually in love with Kuruto

Thankyou for explaining and i'm shocked that aruma is also their brother lol