People of Spira, I thank you for your generous welcome.
Final Fantasy X
Mika first appears in Luca, where he is celebrating his 50th year as Grand Maester by attending the blitzball tournament held in his honor. He introduces Seymour Guado, the newly appointed Maester who has succeeded his father, Jyscal, following his death.
After the battle with Seymour at Macalania Temple, Mika next appears in Bevelle at Yuna's forced marriage to Seymour. Later, when Yuna escapes upon Valefor into the temple, Mika places her and her guardians on trial for Seymour's murder. It becomes clear there is a deep conspiracy surrounding Bevelle and Yevon. Mika is revealed to be an unsent, claiming that even in death, his leadership is "invaluable to Spira".
As Yuna and her friends dig deeper into this web of lies, Mika reveals the truth: "Sin cannot be truly defeated", and the teachings claiming that atonement for the crimes committed during the Machina War can defeat it are false. Only the hope that summoners bring when calming Sin is what keeps Spira going.
Later, when Mika learns that the party have destroyed Yunalesca and the only means of producing a brief Calm is gone, Mika descends into despair and disperses into pyreflies, leaving Spira to its destruction with no intent to witness it. Before vanishing, he mentions Yu Yevon - a significant hint to ending Sin permanently.