Tenchi Muyo! War on Geminar(2009)

Isekai no Seikishi Monogatari

Kenshi —half-brother of intergalactic hero Tenchi Masaki— has been summoned to the mysterious world of Geminar, and his only hope of returning to Earth is piloting a bio-mechanical weapon in a shocking assassination attempt! When the mission fails and Kenshi is captured, he discovers he's been lied to by the very culprits who transported him to this strange new world. Luckily, Princess Lashara kindly welcomes Kenshi and invites him to live amongst her followers. Now, caught up in a political whirlwind —and hotly pursued by Geminar's female population— Kenshi must find a way to get home while civil war erupts all around him!

(Source: FUNimation)