Koharu Seto

Daughter of Hiroko Seto, Koharu is generally a happy and cheerful child who adores her mother. Koharu has been shown to be quite shy and hesitant around others when she first meets them, but eventually warms up to them and begins to consider them as her family, as seen when she drew a picture of Nagi Aiza playing the piano with Kousei Arima.

(Source: Shigatsu wa Kimi no Uso Wiki)