Tenchi Muyo! - Season 1

Tenchi Masaki is an ordinary guy who accidentally releases a demon trapped in a forbidden cave. This "demon" has been imprisoned for hundreds of years, and now she wants revenge! Looks like Tenchi's in trouble! (imdb)

A few days after Kagato is defeated everything returns to normal. Ryouko finds Mihoshi and Sasami reading shoujo manga, which Sasami mistakes as guides on how to win a boy’s heart… Earth style. So Ryouko decides to try out the ideas from the manga to win over Tenchi. But Aeka finds out what her rival Ryouko is doing and tries to take advantage of the same method. Naturally, the results are less than satisfactory for all involved…