Because we've all been hanging out for more bland harem stuff, haven't we?

http://www.animenewsnetwork.com/news/20 ... -confirmed

Tenchi's half-brother is summoned to another world with ancient humanoid weapons

The December issue (on sale on November 10) of Kadokawa Shoten's Newtype magazine will confirm that Isekai no Seikishi Monogatari, the Tenchi Muyo! anime spinoff that has been in development for a decade, is now in production. The magazine confirms the involvement of Masaki Kajishima, the AIC freelance co-creator of the Tenchi Muyo! and Dual! projects. The story is set in an alternate world called Geminar, where countries have fought endless wars with replicas of humanoid Seikishi weapons that they found in ancient ruins. 15-year-old Kenji Masaki, the half-brother of Tenchi Muyo! protagonist Tenchi Masaki, is summoned from another world to Geminar.

Kajishima began discussing his "Seikishi Monogatari" concept a decade ago. According to Kajishima, he had already conceived this half-brother when the original Tenchi Muyo! Ryo-Ohki video series was in development. At the time, Kajishima had planned to work on "Seikishi Monogatari" after Tenchi Muyo GXP, but it has been put on hold ever since. Kajishima wrote in his most recent dōjinshi for the Comic Market conventions that production on "Seikishi Monogatari" is going forward, and AIC posted a teaser website last month.

Source: Moon Phase Comments