Iwasa was considered a highly touted prospect until he lost a bout for the Japanese bantamweight title against future world champion Shinsuke Yamanaka.

Even to Doheny's slight surprise, all three judges scored the fight in his favor, leaving Iwasa without his belt in only his second defense.

[5] Iwasa bounced back in the next fight, called as an IBF final eliminator, by defeating Cesar Juarez via technical decision.

Both fighters clashed heads in the second round that opened cuts for both, but it was Juarez who took more damage in the remainder of the fight.

Iwasa outboxed Tapales for most of the fight, before rocking him with a well-placed overhand left in the eleventh round.