When Toshiie was 5 years old a year after the Fourth Hokage died. The Hidden Leaf Village was under attack by the other villages during the war.
Toshiie was fighting along side his team mate Kakashi Hatake then they were separated by a water style attack. When Toshiie looked where the attack came from he seen a Hidden Mist ninja, it was Kisame Hoshigaki.
Toshiie didn't know if he could take Kisame on equal footing so he decided to use Chidori, but Kisame used Water Shark Bomb Jutsu and stopped Toshiie's Chidori. Since Chidori didn't work Toshiie used Rasengan and Kisame used Water Shark Bomb Jutsu again. Rasengan ripped right through Kisame's attack and surprised Kisame then Rasengan hit Kisame with full force.
Toshiie was trying his best to stop Kisame from getting to the village. Toshiie used everything he had then he passed out, then suddenly Kakashi shows up and hits Kisame with Water Shark Bomb unexpectedly. After Kakashi's attack Kisame disappeared then Kakashi brought Toshiie to the village to get Toshiie injuries healed.
The war was over not long after Toshiie's battle with Kisame. When Toshiie's injuries were healed he asked Kakashi to train him so he can handle an enemy like Kisame and he also asked because Kakashi was an anbu black op. Kakashi trained Toshiie to be faster so Toshiie trained with weights on his legs. Toshiie trained for 3 months with the weights on and Kakashi couldn't teach Toshiie anything anything else. So Toshiie decided to train himself he started training by trying to combine Rasengan and his fire element. After a while of training he learned Liger Rasengan.
Toshiie makes a promise to himself the he will not stop practicing Liger Rasengan until he mastered it. Toshiie Showed Kakashi his new jutsu to see if Kakashi could help him. Kakashi helped Toshiie as much as he could, then Kakashi told him the only person who could help him is Jiraiya and no one knows where he is. So Toshiie asked the Hokage if he can go look but the Hokage already sent someone so the Hokage sent Toshiie to help find Jiraiya.
Toshiie found Jiraiya but he refused to go back to the village so Toshiie made a bit with him. Toshiie said lets fight and if I win you have to come back to the village and if I lose you do what you want. Toshiie used Liger Rasengan because he knew Jiraiya was a sannin and Jiraiya stopped the attack somehow.
Jiraiya asked where did you learn that jutsu and Toshiie said that Kakashi Hatake taught him Rasengan and told him that the Fourth Hokage tried to combine his element and Rasengan but failed. Kakashi also told him that Jiraiya could teach him more about Liger Rasengan. Jiraiya said well it's time for you to master Liger Rasengan are you ready kid. Toshiie said when we're done we're going back to the village. They return to the village 3 years later and Toshiie is now 13 years old and he tells everyone the he must go back to his world to become stronger.
Toshiie comes back 2 years later and is now a soul reaper. Toshiie returns to the see Kakashi again. Toshiie is attacked by leaf ninja while on his way back to the village, he defeats them then more come and one of the ninjas is Asuma Sarutobi. When Asuma gets there he recognizes Toshiie and stops the attack then brings him to the village. Toshiie finds Kakashi training with his new team Naruto, Sasuke, and Sakura. Its Kakashi's new team to Toshiie. Then team 7 gets a new mission and Toshiie decides to help out his old team mate.
The mission is to deliver a special amulet. The first person to try and get the amulet was Kisame Hoshigaki. Toshiie says I'll fight him, you deliver the amulet. Toshiie tells Kisame I'll show you what I learned since our last fight. Toshiie seen that a sword he dicided to use his Zanpaku-to Ikazuchiryu on of the three swords used by the Hitsugaya clan. One is gained by Toshiie Hitsugaya and another was gained by Toshiro Hitsugaya also the last of the Hitsugaya clan. The third swords is unknown. The two swords are Ikazuchiryu and Hyourinmaru.
Toshiie and Kisame were Fighting for a while and Toshiie knew he needed to rejoin team 7. Toshiie needed to finish the fight so he used Liger Rasengan, then hit Kisame and ended the fight. Kisame retreated and went back to Akatski. Toshiie rejoined team 7 and completed the mission. Then Toshiie had to go back to his world and he told Kakashi that he would be back one day so goodbye for now.