Yoshino leads the diplomatic corps for Poseidon. She is known as a quietly chilly diplomat who says few words, but is exceedingly persuasive when she does talk.
She is the equivalent to Olympus' Prime Minister Athena Areios, the two have met several times during an envoy visit to discuss how Poseidon cybernetics technology had been acquired by a domestic terrorist outfit in the city, also in 2138.
Yoshino arrived at Olympus to meet with Prime Minister Athena to discuss the recent terrorist attack committed by cyborgs, whose parts were manufactured by Poseidon. Yoshino denies Poseidon's involvement in the attacks, reasoning that if Olympus boycotts them, then other countries would follow suit and ruin the company's business. As a peace offering, Yoshino presents Athena the control module to Poseidon's satellite system.
Later, after the world security conference, Yoshino departs Olympus. However, her aide, Arguss informed that during the attack on the conference committed by non-cyborg, one of riot said, "I am Halcon." Yoshino was quick to dismiss the possibility of the now defunct research division's involvement.
After the Halcon signal takes control of the world's satellites and through them all Connexus users, Yoshino's water carrier was intercepted by Briareos Hecatonchires, Deunan Knute and Tereus, who wanted to know what exactly was Halcon. Yoshino explained that Halcon was formerly Poseidon's leading scientific laboratory that later became obsessed with mind control, which Poseidon put a stop to after the project lead Elizabeth H. Xander was killed in an accident. When Briareos demanded to know where the centre of Halcon was, Yoshino directed them to Halcon Zero Gravity Plant, where the control signal was coming from. As a sign of good faith, she provides a small taskforce of landmates to assist them. After the ESWAT members departed, Yoshino remarked on the unlikely trio and wished them luck.