Idea Factory re-released today in Japan the Natsuzora no Monologue visual novel game on iOS and Android. You can buy it from the Google Play and the Apple AppStore for 2800 Yen (with tax). The first short scenario is free.

This game is the official smartphone version remake of the 2010 released PlayStation 2 ADV game which later re-released on PSP (2013).
Of course the new smartphone version comes with touch screen support, optimized for the smartphones, fully voiced BUT with the same scenarios.

The game supports only Japanese and Idea Factory is not planning to release it in English.