When you get to Dr. Mad, always say 'No' to him or he kills Mayu permanently. If this happens, turn off the Game Boy Advance and back on. The Here way to his lab is as follows. Walk up and turn left when it appears. Keep walking. Ignore the first cross and keep walking. Next, turn right around a corner, then left. Walk forward and there will be a door. Open it, walk forward, and turn right. Keep walking forward until you reach a corner, then turn left and walk up the stairs.