Overview:

I sneak into my sister-in-law’s room is a touching game using Live2D in which you sneak into your sleeping sister’s room and do naughty things.

Contents:
Basically click and drag to control the game. When you touch an area where interaction is possible, the mouse cursor will change.
Right-clicking on her breasts and nipples will allow you to touch them with both hands.
Right-clicking on other areas will start the auto mode.
You can adjust the auto speed with the mouse wheel.
Right-clicking again will end the auto mode.

To clear the game
You need to drag slowly so as not to wake up your sister.
Drag carefully aiming for insertion.
After that, if you finish cleaning up and leave the room, the game is cleared!
If you drag too hard or don’t finish cleaning up properly, the game is over…

When you clear the game, costumes, cross-sections, and free mode are unlocked.
You can enjoy the game with your sister wearing a different costume.
And you will be able to see the cross-sections of the two parts.
The unlocked free mode can be entered through the title. You can enjoy sex to your heart’s content without worrying about waking up your sister!