Tokyo revengers, 1

Takemichi, a loser who was a gang member in his youth, jumps back 12 years in time to return to high school and save his ex-girlfriend, Hina, who has now been murdered by the Tokyo Manjikai criminal organization. With each time travel, Takemichi influences those around him and slowly changes the past... but will that be enough to save Hina and stop the Tokyo Manjikai from becoming a feared criminal gang?