Japanese fans are worried Sayumi pulled a Kamei. Her name was removed from the Up-Front Create website, which could imply Sayumi left the agency and retired from the entertainment industry. She still appears under H!P OG though.
As a comparison, Ayaya, who has been on hiatus for at least over a year, still appears on the OG and UFC pages. On the other hand, Mitsui, who clearly isn't active right now, is still a H!P member. Only time will tell if Sayumi comes back...