Available as both manhwa and novel.
Mirai Kara no Love Letter: Metsubou suru Sekai no Eiyuu wa Ore!? Una carta de amor del futuro
Also known as: Una carta de amor del futuro · Una Carta de Amor del Futuro Novela · A Love Letter From the Future · 未来からのラブレター〜滅亡する世界の英雄は俺!?〜 · 미래에서 온 연애편지 · Love Letter From the Future · Love Letter From The Future · 来自未来的情书
Ian Ferkus, a 3rd-year at the academy, one day receives a love letter from 7 years in the future. It refers to Ian as a hero, along with the warning that "the world will end if the future is not protected." Now Ian must discover what this future is and how to protect it with the help of his friends.