Yu Yu Hakusho Vol. 17 (manga)

Showdown!!

Yusuke and the gang finally face off against Sensui in a final battle to defeat him and close the portal to the demon plane. The furious exchange of devastating punches and reigun blasts push both Sensui and Yusuke beyond the limits, setting off a transformation that no one, least of all Yusuke, ever expected!

As things wind down from the battle, it's time to tie up a few loose ends. Then just when it looks like Yusuke might get some time off for a change, another message from the demon plane arrives that will set Yusuke's final destiny in motion! But first Yusuke needs to ask Keiko a very important question...