What if a younger girl wants to take care of "you"?

The protagonist lives alone after getting transferred to a local city. One day, he met Hiiragi Isana, a girl who has problem with her bicycle.

As a gratitude, Isana who learned protagonist's circumstances offered to taking care of him. Thinks she said it as a courtesy and won't actually happen, the protagonist casually agreed, but...

Isana actually came to his home and taking care stuffs like meals and cleaning. Then, while playing together and taking care of Isana's study and other stuffs, the distance between them got closer and closer.

The new throbbing daily life with younger girlfriend starts.