Devil Master was a Gold Pet, which was a more expensive Digital Pet with superior properties to a regular Digital Pet. Kujirada stole it from a shop.
Kujirada tried making Devil Master stronger in order to win a competition. He did this by swiping other people's pets and feeding them to Devil Master. Among Devil Master's meals were Sumomo-chan and Joe. Kujirada tried to feed U2 to it, but Hiroto Honda arrived, after spending three sleepless nights taking care of Super Strawberry. Honda connected Super Strawberry to Devil Master and Super Strawberry swept Devil Master away.