Isekai Shoukan Ojisan no Juu Musou Life: Sabage-zuki Salaryman wa Kaisha Owari ni Isekai e Chokki Suru

The middle-aged airsoft enthusiast Daisuke Koga is summoned to a another world on his 40th birthday. Given the ability to turn airsoft guns into real guns while traveling back and forth between two worlds, Daisuke must find a way to save the other world. Alongside the lady swordsman Rena, Daisuke becomes the only gun user in this fantasy world, and he will come to dominate it with overwhelming firepower every day after work!

(Source: Houbunsha, translated)