Senya Ichiya Monogatari

Both are entries in Tezuka's trilogy of experimental adult-oriented films, Animerama. The eroticism and mature humor are similar, and the production teams have a huge staffer overlap. 

They're actually not similar in terms of plot or theme, but they are both part of the Animerama trilogy, which consist of three rare adult-rated films. The Animerama films were produced by Mushi Productions during the late 60s and early 70s, which was founded by Osamu Tezuka himself.  

Both have a similar art style and heavy sexual overtones. Both also have a bizarre story.