Venus Mission - Moto Koroshiya de Youhei no Chuunen, Yuusha no Ansatsu wo Iraisare Isekai Tensei!

A former hitman and mercenary is reincarnated in another world to take on a mission to assassinate thirty-two heroes. Suzuki Takashi, 42, dies of illness, but his aptitude for assassination leads a goddess to bring him into a new life in a different universe. There, Takashi faces the heroes with the advanced combat techniques he learned in his past life, the traditional Shingu-ryu martial art, and powerful magic he has only just discovered. A fantasy of magic, swords, and firearms begins as he takes on his daunting targets.