Yes, TOOL plus ツール ( Pro 日本語版 ) ¶ is completely free and it doesn't have any in-app purchases or subscriptions.
Not enough reviews to make a reliable assessment. The app needs more user feedback.
TOOL plus ツール ( Pro 日本語版 ) ¶ is free.
To get estimated revenue of TOOL plus ツール ( Pro 日本語版 ) ¶ app and other AppStore insights you can sign up to AppTail Mobile Analytics Platform.