After receiving Impmon as a tamer, Ai and Mako would often fight each other over taking or breaking each others' toys, and pulled Impmon's arms to make him take their sides. From here, Impmon left them and hated humans.
When they received a small dog, they fought over it as well.
However, by the time Impmon returned, they had decided not to fight anymore, knowing this was the reason Impmon left. As Impmon left to help the tamers fight the D-Reaper, Mako gave him a toy gun which was later transformed into the Corona Blaster when he became Beelzemon. Later, he and Ai received a Digivice and became his tamers, and were introduced to the others.