SakiTomo 1 (Patreon)

Upon his wishes, Tomokazu has embarked on a new step in his life as the Apprentice and Server to the Shrine Priestess, his older sister Saki. At age 17, Saki would be inaugurated as the true Priestess of the Island in the Underwater Shrines, which Tomokazu must attend throughout. First he must dramatically improve his breath holding skills - which Saki had already accomplished earlier in her life as the heir apparent to the Princess Priestess.

(See Tomo? My heartbeat has slowed down.)

(Yes, Sis...)