Venus Mission: Moto Koroshiya de Youhei no Chuunen, Yuusha no Ansatsu wo Irai sare Isekai Tensei!

The request from the goddess is to assassinate 32 heroes!? 42-year-old Takashi Suzuki is a former hitman and mercenary. Although he died of cancer, he was reincarnated into another world due to his potential as an assassin. He uses the modern combat techniques he developed in his previous life, the ancient martial art "Shingu-ryu," and his newly acquired powerful magic to face off against the unrivaled heroes. An exhilarating fantasy of swords, magic, and guns begins!!

(Source: Kadokawa, translated)