how can i get unicorn ehehehehehe

If nanami is dead she is dead you can't revive him... If you want that nanami will not die... Collect all the 108 characters before nanami's death...

I found you.about suikoden 2 you seem to know alot I've found rokkaku and would I be able to recruit mondo and the others with valeria??? Because they keep kicking me out of there village do I need kasumi?

There's no way to recruit all of the 108 characters before Nanami's death.

Lore-wise, she never does die. She runs from Riou because she realized shortly before deploying that her presence only made things more difficult for Riou to help the Orange Army to succeed.

The only way to actually SEE that she runs away is by, indeed, collecting all of the 108 Stars of Destiny by the end of the game.

There is no absolute time limit besides those absolutely implied by such characters as Elza, for instance.

You can get sigfried the unicorn from the forest behind the kobold vilage during tengaar and hix subquest but you must have recruited badeaux so you have a trinket that can here sigfried or you can never recruit him