You run around as Shujinko and the story is based on him. However when you enter a fight you transform into a different character whom you train with. Later on in Konquest it is random on which character you fight as.

I think you can morph into other people during battle only.

i didn't got that. can you fight as young Sujinko or you always morph coz i saw a movie where young Shujinko fights Bo Rai Cho

thats one of the begining training levels where you play as young shujinko.