Tenchi Muyo!: War on Geminar

Kenshi Masaki is a 15 year-old boy that unwillingly traveled from his home on Earth to the alternate world of Geminar. In Geminar, the countries wage wars using Sacred Mechanoids, humanoid weapons that were originally discovered within ancient ruins. 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.