you and fumihiro are brothers and sisters who live in a country called "seinaru kuni" one day you swim with fumihiro in the river, which is clean and sparkling You enjoy the river by playing in the water, while Fumihiro just soaks and stays quiet

"nii-chan? come play in the water with me" you say

fumihiro just calms down and focuses on his hair being spilled by a waterfall that's not too strong