Ore no Isekai Shimai ga Jichou Shinai!

Yuya remembers his sister's final words, urging him to live freely and find happiness. He contracts the same illness she did and dies without fulfilling her wish—until he awakens in a new world. Confused but determined, he resolves to honor the promise he made to his sister. Reborn as Lyon, the second son of a noble family, he begins a new life. However, as the child of a mistress, he is separated from the main household, denied an education, and arranged to be married. Frustrated by these constraints, he questions how he can pursue happiness. His perspective shifts when he meets a girl, setting in motion a story about a boy seeking joy and reconnecting with his sister's legacy.