Knowing Vergil, he likely thinks its some ridiculous and foolish holiday that he doesn’t get at all. In the beginning, he dismisses it as just another piece of random human foolishness and childishness. That being said, when you do bring it up to him and try to get him to share some pocky with you, naturally he’s reluctant about it.
Not that that stops you and your mission of course since you’re determined to get him to play at least one round of the pocky game together. You even brought a variety of flavors out ranging anywhere from classic original chocolate to green tea, mint, strawberry, orange to even cheesecake pocky.