Natsume is teasing something River City Ransom-related. The publisher posted an image of question marks on Twitter, with the text, “Punch! Kick! BARF!”
“Punch! Kick! BARF!” is a River City Ransom thing. In the English version of the game, the line romanized as “Geh!,” which is supposed to symbolize someone coughing up or saying “Argh!,” was translated as “BARF!”
As for what Natsume is teasing, there are a couple of possibilities. It could be River City Ransom SP, a remake of the original Nintendo Entertainment System game, which is due out in Japan on June 2. Or it could be Downtown Nekketsu Jidaigeki, a spin-off set during the Edo period, which is already available in Japan.