Spinning Tropics by Aska Mochizuki

When Yun becomes one of Hiro's students, they are instantly drawn to each other. Hiro is a young Japanese woman who has recently moved to Vietnam to be a language teacher, and Yun is a shy, young Vietnamese woman studying Japanese, determined to make a better life for herself. For both of them, it is their first time in love with another woman. But when a businessman befriends Hiro, Yun grows jealous, and a complicated love triangle forms.