WTH-001 - My little sister and I on a hot spring trip, 8 hours of non-stop action

Since the actress names aren't clearly listed in the streaming version, you're better off buying the individual videos of the actresses you like. The theme of this series is the younger sister's aggressive seduction, and her desperation feels very real. Even if you don't have a sister, you'll get sucked in. However, the footage is a bit dated, so it might be hard to watch. The premise is the same as other 'sister hot spring trip' series, so I'd recommend checking out the newer, updated versions featuring your favorite actresses.

There are plenty of actresses, but the footage is so old that it feels like it kills all their charm.