Tenchi Muyo: War on Geminar [OVA]

Kenshi Masaki is a 15 year-old boy that has unwillingly traveled from his home on Earth to the alternate world of Geminar (? Jemin??). On Geminar, the countries wage wars using Sacred Mechanoids, humanoid exoskeletal weapons that were originally discovered within ancient ruins and developed over centuries. After being tricked by a mysterious organization into participating in an attempt to assassinate Lashara Earth XXVIII, the young princess of the Shtrayu Empire, he ends up captured after he chooses not to kill her. When Lashara hears the truth, she decides to help.

Disguised as her attendant, Kenshi travels with her to the Holy Land, a virtually impregnable fortress that serves as an academy to train Sacred Mechanoid pilots, most of whom are female. With his kindness, tenacity, and skills that vary from carpentry to advanced techniques of survival, Kenshi eventually becomes a celebrity in the academy, becoming the object of affection of many female students and making some of the male students envious. However, the same organization who deceived Kenshi is secretly working inside and against the academy, and a worldwide conflict is about to begin.