Well there was a plan for Oshiri village to appear in this game but it was scrapped. Now it will be accessible during festival time(past version) after a mission. Len's game is cancelled like other erotic projects.
Lady Merusa is Goddess of true love. After corruption, she gets power with growing number of unfaithful people in the world. She only wants her and her lover to be only faithful entities left. Having anal or oral sex in her shrine makes her more powerful that's why she has influence the village people to arrange such festivals.
Well in Magic Ring, you will be able meet Mrs. T at Sayuri's home and she sometimes will come to Sunflower city with Sayuri to meet Masuo. She will live at an undisclosed location and will message you when she is in the city.
It was going to be unlocked after getting a message from Sawako but I used Tsukiko's room instead.