Isekai no Seikishi Monogatari (異世界の聖機師物語) or Tenchi Muyo! War on Geminar in translation, is an OVA anime series created by Masaki Kajishima which is a spin-off of the Tenchi Muyo! series. It was produced by AIC Spirits and BeSTACK, totaling up to thirteen episodes aired on Animax between March 20, 2009 and March 19, 2010, which was later licensed by Funimation.
A light novel adaptation by Atsushi Wada was published by Fujimi Shobo on August 20, 2009 under their Fujimi Fantasia Bunko imprint followed by a manga adaptation serialized in Comic REX and published by Ichijinsha on June 9, 2010, spanning two volumes.
Kenshi Masaki, a 15-year-old boy and younger brother of Tenchi Muyo!'s protagonist Tenchi, was unwillingly traveled from his home on Earth to the alternate world of Geminar, where the countries wage wars using Sacred Mechanoids, humanoid exoskeletal weapons discovered within ancient ruins and developed over centuries. After being tricked by a mysterious organization into participating an assassination attempt on Lashara Earth XXVIII, the young ruler of the Shtrayu Empire, he ends up captured after choosing not to kill her. In return, Lashara decides to take Kenshi under her protection for the latter's curiosity and unique abilities.
Disguised as her attendant, Kenshi travels with her and her bodyguard Chiaia Flann to the Holy Land, a virtually impregnable fortress that serves as an academy to train Sacred Mechanoid pilots, whom the majority of the students are female. With his kindness, tenacity, and skills that vary from carpentry and cooking to advanced survival techniques, Kenshi eventually becomes a celebrity in the academy and main affection of many females, and earning the envy from most of the males. However, the same organization who deceived Kenshi is secretly working inside and against the academy, where a worldwide conflict is about to begin.