Dissolution
~ On September 22nd 1997, X Japan officially announced its separation; anouncing at the same time its last concert 'The Last Live' on the next December 31st. ~
         From what I've heard, Toshi would have been at the root of all this sad event.  During an interview on June 1997, Yoshiki (X leader) said that Toshi would have been a vicitm of a sect in Japan. In 1997, Toshi married the actress Kaori Morisumi, which was already part of the 'Remuria' sect.  The worst about this mariage is that Kaori hates everything about X.  When this famous mariage has been officially announced, Kaori would have been harass by some X fans.  Under his new wife influences, Toshi took part of the cult.  I've heard that the sect guru would have brainwashed Toshi, telling him that he is just a puppet for X (Yoshiki?).
"Toshi's saying that everything is okay, but he has changed"
- Yoshiki
        Toshi once said on TV : "(...) I'm ready to die if hide had not committed suicide."  Its the most horrible thing he has ever said.  By now, Toshi deny everything about X and Toshi with X.  Everyone knows that he already sold many of his costums that he once wore on concerts.
~ Another reason for its departure ~
       Toshi was tired of everything about showbusiness and X.  Yoshiki once admitted that hide and he has done everything to change Toshimitsu Deyama into Toshi.  Toshi wasn't done to become a rockstar and live like an artist.  Just remember that he wanted to became a doctor...  Yoshiki and hide always taught him how to speak, how to dress, how to make up, how to sing and be on interviews and concerts.  Yoshiki confessed that Toshi was pretty tired of this lifestyle, which was killing his  own true self.   

          During a concert, to slowly announced his departure from X, Toshi killed himself  on scene (theatrically).  Next, he ceassed his excentric hairstyle, to adopte a more classical look.  Then he said on an interview : " (...) I need changings, I wanna be a singer ''

          Yoshiki could not believe that Toshi had left the band.  He could not bear to replace Toshi's part in X Japan, so it was decided that X would disband.  Yoshiki and hide had the intention to reform X on 2000 with hide on vocal... but unfortunatelly, you know the rest of the story ; hide died on 1998, killing at same time Yoshiki's hope.

          To end this really sad story on a more positive way, let say that Pata, Heath and I.N.A formed a band named DOPEHEADZ.  I know, this is not X, but still...
~ Thanx to Issei for its precious infos ~