I’m looking for ether a manga or webtoon about two brothers (Maybe step brothers, I believe?) the older one had light brown hair and I think he kind of looked like a young Makoto from Free. He was well liked in school also. The younger one had black hair and was obsessed with the older brother. It got really dark at some point, the younger one wanted all of the older brother’s attention and I think he killed his pet goldfish out of jealousy and despite being scared the older brother said it was okay and comforted the younger one.

That’s all I remember apart from the ending where the older brother gets killed on the road somehow and the younger brother ends up in a jail cell, happily fantasising about the older brother alive and being with him.

Quote from susubeansu

...

Oh, it was An Uncomfortable Truth.