If you loved Keizoku: Unsolved Mysteries - Beautiful Dreamer, try 12 Suicidal Teens
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.
What they share
Both films are directed by Yukihiko Tsutsumi, and they both carry the slow burn mood tag, and they sit in Drama / Mystery territory. If that's the register that drew you to Keizoku: Unsolved Mysteries - Beautiful Dreamer, the second film will land in a comparable space — through a different lens.
slow burn
What 12 Suicidal Teens is
Rain on the hospital skylight. Twelve young souls arrive, each carrying a death wish and a number. One extra body lies on a bed. The would-be suicides become accidental detectives, unraveling a mystery and each other's secrets. A locked-room premise with J-horror undertones.

