Doing nothing in Omori is good practice for The HIKIKOMORI Route in Omori. You play through the prologue as you normally would in the dream world until you wake up in the house as Sunny for the first time. Go through the part where you defeat Sunny’s anxiety going down the stairs, eat the cold steak, and go to the bathroom. Once you finish in the bathroom, you’ll hear a knocking at the door. Normally, when someone knocks, you answer, but in this case, you do nothing.
If you want to start The HIKIKOMORI Route in Omori you have to select the “Do Nothing” option when Kel knocks on the door in the next chapter. “Mari” will make you feel bad about it, but in doing so, you won’t get the bathroom scare. Not letting Mari in will not affect the Omori Hikikomori Route.