This stage is a very nasty multi-level maze. There may be better routes than the one given here, but this one works, and doesn't leave anything very important out.
Head east. The second hawk will drop a heart, so it's worth killing. When the path turns south, enter the turret instead. Head due south and out again. Follow the ledge round to the left, onto the next screen, then head south and take the last entrance on the left.
In here, making sure you stay on the upper level, head south, jumping over gaps. (If you fall down, you'll have to leave by the exit right at the top; then follow the path back northeast to the turret you entered before.) Take the lowest exit on the left-hand side out. Now head round the ledge. Ignore the first entrance for now, and head along to the next one. It's quite a long way. Go inside and kill the ninjas, then smash the chest against the wall to get the bracelet. Equip it. Go back outside and to the entrance you just ignored, at the west end of this ledge, and go inside and up the stairs.
The hawk which attacks you here will drop meat when you kill it, so do so if your health is getting low, then head east. The first entrance hides nothing but some rats. Take the second, and go up the stairs, then to the west. On the next screen, there are three ninjas: one attacks you as you enter, one is waiting on the mesh bridge to the north, and there's one beyond that who drops a heart when you kill him. You'll see him from the upper floor if you miss him.
When you've got the heart, head to the upper floor, and again go round to the west, exiting to the south. Go west, and in through the next entrance. You want the passage that branches off to the right; follow it to the end, and you'll come out outside again. Take the entrance to your left; inside go down to the lower floor and out again, then in again through the other opening. Up the stairs, jump up the larger steps to the upper level, and go round to the right and up the passage to the door. You'll come out on a wide causeway; follow it up and right, and go inside again.
Head to the top left of this screen, and take the stairs up. You'll emerge on a broad rooftop; head to the very north, and up the steps to the tower. When you go through this final door, you'll find yourself back in Secia's room.
After all that, leave the room and head north. You'll automatically go to the throne room. When you regain control, keep trying to attack your opponent – don't worry about your health, you're meant to run out. When you do, another scene will be triggered.