Oshiire no Naka no Dungeon Craft: Koufukude Fukoude Koufukuna Kyoudai

A high school student named Toru Shiina discovers a dungeon portal inside a closet in his dorm room. The dungeon resembles a vast video game world, and at its center, beneath a large tree, he finds his deceased younger sister, A-chan, who had died in an accident as children and was never found. From that point, the two of them take on the role of the dungeon's caretakers, overseeing its development. Toru returns to the dungeon once more to see A-chan, uncertain of what awaits him. The story explores themes of happiness and hardship, focusing on the pursuit of joy.