This was wonderful; I loved the idea of Hikaru feeling he needed to "borrow" Akira's go, and then reverting back to his own. I'd never seen something like that before, and it was refreshing.
Your writing is excellent, and the characterization was spot-on-- even the OOC when Hikaru was "being" Akira was believable, so it wasn't actually OOC at all. You did a great jobs with Hikaru's dialogue, too; I find a lot of authors end up writing Hikaru's dialogue as stilted or overly child-like, but you did great.
I also couldn't help but notice the date at the end of the story-- now Hikaru will have a happy memory for that day, not just a sad one. Yay! ^_^