My Isekai Life 15 (manga)

A seemingly unending horde of monsters threatens to take over Evildominus Island thanks to a mysterious cursed tree. Yuji must figure out a way to save the adventurers from a grisly fate without letting anyone find out about his powerful magic ability! While doing so, Yuji receives an unexpected letter from Father Steyl, giving him a convenient cover story for the extraordinarily powerful spell he’ll need to wipe out the monsters and protect the precious fertilizer, Mother Earth’s Tears. But will his magic be enough to dispel the curse that shrouds the island?