What My Brother Doesn't Know

The main character, Yuzuki, has a kind dad who’s been living away from home for work.
Every month, Yuzuki and his younger brother would visit the apartment where their dad lives alone.
But whenever his brother wasn't looking, Dad would always sneak in a few slightly naughty things with Yuzuki...
“I want him to do it more…” Yuzuki finds himself developing feelings for his dad….
One day, by chance, the three of them—Yuzuki, his dad, and the brother—end up taking a bath together for the first time in a long while…

Official English:
DLsite, BOOTH