Gisou Furyou is a Manga/Manhwa/Manhua in english language, Manga series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

『If it’s discovered that I’m not the strongest (real deal), I’ll die…!?』 Takashi Yamazaki, who was bullied daily. The one who helped him was the strongest delinquent, Kurogane Ren. Yamazaki admired Kurogane, but one day, when he woke up, he found himself in the body of Kurogane Ren. And in front of him was the corpse of Kurogane Ren and a mysterious message… 'If you don’t want to die, take the top position at Reimei Academy.' To return to his original body and find out the truth behind Kurogane Ren’s death, he challenges the most ferocious and worst delinquents to a fight!