After unlocking the locked door with the cat in it, I've gone doen the stairs and through the next door. After, I went as far right as I possibly could, until I found a door that's not opening. Every walkthrough I've read says that youre just supposed to walk right through that door, to get towards a room where Inuyasha says something about 'smelling human blood'. I've already used the Key, and it's gone from my items afterwards.

I've gotten past this part before when I got this game, but I haven't played it in so long and someone erased my memorycard.

How do I get past this door??