[Inuteikoku (Mura)] An older brother who helps her futanari sister masturbate

A big brother has shared baths with his little sister since they were kids, never minding the cock between her legs—until the day she shyly asks to see his in return. What she reveals is an absolutely massive erection, far too thick and heavy for her to relieve by herself, and she sweetly enlists her flustered sibling's helping hand. One twitching, gasping climax later, her huge shaft drenched in cum, she makes him promise to keep assisting her whenever she needs it.