Futago no Imouto ni Korosareta Ane, Nidome no Jinsei wa Hatsukoi no Ike Oji Outei ni Full Bet Shimasu!

Synopsis

Diana, who was murdered by her twin sister, finds herself transported back in time to the morning of her graduation ceremony. She begins to fight to save Alan, her first love, who lost his life in her previous life. The romance fantasy about a young lady who met a tragic end and gets a second chance at life, featuring a significant age gap, begins.(Source: Bushiroad, translated)