Isekai Munchkin: HP1 no Mama de Saikyou Saisoku Dungeon Kouryaku

Depicting the story of a shut-in, Yukito Kirihara, after being reincarnated into another world. His peaceful life with his precious caring sister, Sana, suddenly come to an end when a beast appeared and attack them, thus reincarnating him into the Ever World. Moreover, knowing that Sana also got reincarnated into the Ever World, for the sake of finding his beloved little sister he begins his journey in another world.

(Source: Endless Journey)