Together When... is currently in fourth position in iTunes Japan's "Top Songs" ranking.
Ranks
#1 EXILE - I Believe
#2 Tokyo Jihen - Senkou Shoujo
#3 RIP SLYME - Tales
#4 Ayumi Hamasaki - Together When...
#5 Ne-Yo - Do You feat. Utada Hikaru
Remembering that the release was just yesterday (or today lol) and probably the song will become more popular soon 
And, who want to buy the single in iTunes, the link: CLICK ME