Rina and holes (Rina and Ana)

You can say "legendary Studio" Ivory Tower (FuwaKumi, Mix Peace, Nana's daily work) after 5 years of silence returns in 2018 with a new work "Rina and Ana".  The main character of the hentai girl named Rina-Chan played on the Playground late at night and trying to save his phone, stuck in one of the holes. Then out of nowhere there was a depraved boy and took advantage of the situation...