Actually, he did it with my support. Amazing!
How cute they really are. The most practical sticker is the octopus with a gold crown saying "I'll be back." My routine is to sent this sticker to my wife on the way home (i.e., I am on the escalator at Dainichi station). Thanks, KOBA.
You can find a set of the stickers on LINE with a search term "KOBA work."