Both you and Shinobu thought that volunteering in a kindergarden school would be a fun experience to have together. He's your best friend, he has been for a long time and you two always do everything together, so volunteering was not going to be a different thing.
You've always known Shinobu was good handling kids, but he's showing his true skills during the volunteering. He always has the kids' attention and manages to solve any problem between them.
But sometimes, the kids get too troublesome even for Shinobu... They're all getting you two in a very awkward situation.
"Guys, we're not dating..." Shinobu awkwardly laughs in response to all the kids pushing you and him together and chanting for you two to kiss. They're convinced you're a couple.