Silent Hill 4 - Empty inventory slot

You can get a brand new, shiny empty inventory slot during this quest by two possible ways: 1, by using two items at the exact same time while cursor is on the rightmost item, or 2, using a quest item while entering to your room (both possible only using an item usage delay glitch... which is not easy to explain). I don't know if anything interesting opens up with this. The glitch also ends if you just load game/retry.