The Legend of Heroes: Trails of Cold Steel

Based of the video game by the same name Eiyuu Densetsu: Zero no Kiseki.

After the disaster that devastated the entire Erebonia Empire, the Great Twilight, the continent of Zemuria escaped crisis thanks to the efforts of its heroes, but was still in chaos. "The Hermit C" who wrapped his will in a mask, the young men and women, "ex-assassins", who escaped from a special organization, Swin and Nadia, and the strange "Rosenberg Doll" who has the appearance of a girl. The party, which is tied up with a special connection, sets out on a journey with their own expectations in mind. What awaits at the end of the trip!? (Source: Falcom, translated)

A 4-koma slice-of-life comedy manga in which characters from various games released by Falcom (e.g. Dragon Slayer, The Legend of Heroes and Ys series) come together in a school.