Saikyou Shoukanshi wa Around 30 Ossan: Card wo Oya ni Shobun sareta Card Gamer no Isekai Musou

Sousaku Kamifuda, a card gamer who, even at 30, continues to enjoy the same otaku lifestyle he had as a child. While his fellow otaku friends progress through various life stages, leaving him isolated, his mother sells off his precious collection. Before he can even process his despair, he's suddenly transported to another world. Though initially at a loss, Sousaku discovers that his otherworldly transfer has granted him the ability to turn monsters into cards and summon them. After using this power to save two girls from a monster attack, the middle-aged card gamer's conquest of this other world begins...!! (Source: Ichijinsha, translated)