On his official instagram, Takeuchi Ryoma mentioned that ending pose he did was made by Sana~

Ryoma is the male lead for "Sensei Kunshu" and TWICE sang "I want you back" as an OST for the movie. Check the version of TWICE with the cast here (also, you can see Ryoma's final pose made by Sana in the vid):

[There should be a GIF or video here. Update the app now to see it.]

I'm happy that our girl got a cute promo from a Japanese celebrity as well~ ❤️