If you loved The House Where the Mermaid Sleeps, try 20th Century Boys: Beginning of the End
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
You already loved

The House Where the Mermaid Sleeps
→
Try this next

20th Century Boys: Beginning of the End
What they share
Both films are directed by Yukihiko Tsutsumi. If that's the register that drew you to The House Where the Mermaid Sleeps, the second film will land in a comparable space — through a different lens.
What 20th Century Boys: Beginning of the End is
Summer 1969, a secret base, a rusty bike bell. Kenji and friends battle villains in their imaginations, recording them in a book. Director Yukihiko Tsutsumi brings 90s Japan to life.