Totonoi.

Totonoi is a nature-sound app designed to deepen your calm during sauna time.
Just play it in the sauna, during rest, or outdoor cooling. Gentle ambient sounds reduce distraction and help you settle your breath and mind.
It also works nicely as minimal background audio for focus, reading, or sleep.

— Sounds included
Rain / River / Forest / Fire
Harbor / Waves / Insects / Grassland / Bubbles (some are Premium)

— Features
• Simple, seamless looping playback
• Sleep/sauna timer for automatic stop
• In‑app language: English / Japanese / Finnish

— Premium (auto‑renewing monthly)
• Unlock premium nature sounds (Harbor, Waves, Insects, Grassland, Bubbles)
• Priority access to future sounds
• Cancel anytime in iOS Settings > Apple ID > Subscriptions

EULA（https://www.apple.com/legal/internet-services/itunes/dev/stdeula/）