About
Built for users who expect better.
Kuroki Studio builds paid Android apps. Every product in the portfolio reflects five non-negotiable principles: not marketing claims, but constraints on every feature, every dependency, every architectural decision.
Five principles
One-time purchase.
Users own what they buy. Pay once and the app is yours, including all future updates within the major version. No core feature is ever locked behind a recurring fee. A subscription appears only where it funds genuine ongoing value (a live service with real running costs, such as online multiplayer), never as a default, and never just to generate recurring revenue.
No advertisements.
No banner ads, no interstitials, not on the first launch and not after. Advertising requires tracking. Tracking requires data collection. Neither belongs in a utility app.
No accounts required.
There is no account, no server to sign up for, no email address to hand over, no password to forget. Every app installs and runs without a sign-in.
Local data only.
Your personal data stays on your device. No cloud sync, no analytics, no telemetry, in any app. The utilities never touch the network except to verify a purchase. The one exception is online multiplayer in Barrage, which relays only ephemeral match data between two players for the length of a game, never stored and never tied to you.
Polished, modern UI.
Material Design 3 for Android. Clean, purposeful layouts without decorative clutter. The interface is the least interesting part of the product. It should get out of the way.
Context
The gap Kuroki occupies.
The Android paid-app market sits between technically excellent FOSS apps most users have never heard of, free ad-supported apps that treat attention as the product, and subscription apps that charge monthly for tools people use daily.
Kuroki occupies the gap: Play Store presence, one-time purchase, no ads, no account, polished UI. The same audience that pays for indie iOS apps. Underserved on Android.
The name
Kuroki (黒木)
"Black tree" in Japanese. The logo carries that metaphor: deep roots (foundational, durable), bare branches (no excess, structural honesty), surviving form (built to last, not to chase trends). Two syllables. Pronounceable everywhere.