From what we understand Hosokawa has vacated the belt due to being in poor physical condition. We're not sure what sort of condition this means but from what we're hearing he will be returning to the ring if he can recover, which suggests to us there is a medical issue.
With Hosokawa having vacated the belt we will now see Nonaka fighting against the big punching Kengo Nagashima (14-10-2, 13) on August 10th. The bout certainly isn't as evenly matched as the one we had been expecting but should be a more exciting proposition courtesy of the power of Nagashima.
Sadly for Hosokawa this sees him giving up the title he won in March, when he beat Tadashi Yuba, without being able to make a single defence of the belt. Considering the effort he made to win the belt we can only feel sorry for the way he's had to give it up. Hopefully, if he returns, he will be able to fight the winner of Nonaka/Nagashima for the title sooner rather than later.
(Image, courtesy of boxmob.jp, shows the now out of date poster for the fight featuring both Nonaka and Hosokawa)