light kun

Hey there! I have this anime watched last year but I didn't note the title 'cause I became busy after watching it. The plot is the mc (boy) has a brother who died when they were young but their mother can't accept it and became depressed. So in denial, the mother treated the mc as his little brother and the mc agreed to it because they had aj agreement with his father. However, the mc feels like he has no identity because of that. Can someone please tell me if you know this anime. Been dying to know it since last year. I was so hooked up to it that I keep on searching it on every sites possible.