The Dragonkin Girl I Picked Up Is the Third Dragon Princess

Picked Up the Third Dragon Princess and Was Sent to the Border to Marry into the Dragon Clan

Basically, it's a story about reincarnating in another world, meeting a beautiful childhood friend who pilots the war mech "Ruin" across the battlefield, becoming best friends with the youngest archmage in the demon race, and enjoying the protagonist's halo while only wanting to graduate smoothly and become a corporate drone in another world. Unfortunately, he picks up the Dragon Clan's Third Princess, who loves steamed buns, and from then on gets sent to the border front to marry into the Dragon Clan.

Pure sweetness, absolutely no angst, so enjoy without worry. Cross-dressing guarantee. Extra chapters for monthly votes.