Looking for a yaoi I can't remember a lot about.

I really only remember one specific part, but I'm hoping the detail's enough for someone to know it

I think it counts as bara. I remember the guy being a coach, he buys a dolphin shaped prostate massager, can't get it back out, and a student shows up while this is going on. That's really all I remember, but it was a good read so I'd love to find it again.