I have replayed this like 20 times already, I can't get enough of how cute Karma is and it feels so good to know Koro-sensei got the shy side out of him. He's so cool and calm in front of class 3-E but this proves he can get embarrassed quickly.

Hehehehehe~ Love this scene so much. And I'm literally telling you this is freaking cannon. Last Friday's episode proved it. Karasuma gave Irina that rose with no influence at all in the end.
Though I can't find a clip.........

If this doesn't prove it's canon then I don't know what does. It was all a little hinted and nothing really happened but Karasuma did call the 'new move' impressive.