Bad Ending: Collect all 24 Effects, then leave Itsuki's Room.
Glitch Ending: Collect all 24 Effects, then go to bed. Enter Doodle World, then find a broken door. Heal the door with the Healing Aura Effect, then enter it to get to the Lake. There, drop all of your effects, then wake up. The next time you go to bed, the Nexus will be glitched. Enter the only available door to get to a glitched version of Itsuki's bedroom.
Leave the room to get to the Glitched Hallway and navigate it (it's fairly straightforward). Go through the left door in the room you end up, then go through the central door in the Alternate Nexus; gain the Baku effect as detailed in the good ending guide, then allow the glitchy advancing wall to catch you.
Good Ending: Collect all 24 Effects, then go to bed. Enter Doodle World, then find a broken door. Heal the door with the Healing Aura Effect, then enter it to get to the Lake. There, drop all of your effects, then wake up. The next time you go to bed, the Nexus will be glitched. Enter the only available door to get to a glitched version of Itsuki's bedroom.
Leave the room to get to the Glitchy Hallway and navigate it (it's fairly straightforward). You'll end up in a room with two doors. Enter the one on the left. Enter the door at the end of the hallway. Go into the central door of the Alternate Nexus you end up in to get to the Dream Steps, then walk up the stairs there and interact with the Teru Teru Bozu-like NPC to gain the Baku effect. Leave the area, and go back through the door you came from. The room with glitch out and an advancing wall will appear. Leave the room, navigating the barriers to the best of your ability. You will end up back in the room with the two doors. Enter the one on the right.
Go up the hallway and watch the cutscene that plays out. After waking up, leave Itsuki's room.