Ivan Larzalev was one of the products of the Imaginary Numbers project in Front Mission 3. He was also one of the few Imaginary Numbers to be a 'failure'. As Imaginary Numbers are intended to be perfect, he was hunted down by the others, and managed to stay alive until a certain point in the game.
In Emma's storyline, player met Ivan in a Hua Lian rebel base where he intended to leak information about genetic engineering project involving Bal. He died by the attack of squad of Imaginary Numbers lead by Rosavia Gray, when he tried to protect Emma from the enemy attack.
In Alisa's storyline, the player met him in a civil airport. Hei Fong Liu noticed him as Imaginary Numbers. Ivan who got witnessed escaping the city with rebel force intended to eliminate them so he could avoid being chased by Imaginary Number. The party didn't know what would Ivan do. The party had to put him down as he went out of control.
Both events occur when the player party reaches the middle of Da Han Zhong story arc.