Sure thing, candy_boy!
Sayu definitely said that she ate out and did other things with Riho after the graduation but she didn't indicate whether it was just once or multiple times.
Aw... I hope they're in contact even now, more than a year later. Looking forward to how their relationship would have evolved come Riho's return. Though I did quite enjoy the predator-prey thing they had going on. lol
Also, I read on Twitter that Sayu talked a bit about Riho again on her TV Bros mag interview released yesterday. No online copy has turned up yet tho.
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Meanwhile, some other belated Riho or Riho-related stuff:
Ooops, almost forgot!
On this day, exactly six years ago, was the release of Maji Desu ka SKA!
9ki's debut single 6th Anniversary!
ひゃっっほ~い♪( ´θ`)ノ