Yuasa is a caring individual shown by how he treats his family and client. However after Jun's transformation, he grows very concerned for her to the point of infatuation with his relationship with his wife and daughter beginning to strain. He even went to find Jun during a Devil Beast attack while his family was evacuated.
Yuasa had worked with Jun since the start of her career. After Jun became Devilman Lady, Yuasa began to grow very concerned for Jun and even fell in love with her. He would often be on the sidelines while hoping Jun would be alright while Yuasa's relationship with his family starts to spiral downwards. As such he would never succumb to his desires including an extortion scheme of Shiro Sakazawa. When a Devil Beast outbreak occurs, rather than stay with his family Yuasa instead tries to find the missing Jun. Finding Jun, he confessed his feelings for her. Jun however told him to stay with his family as she believed her path was one that she must do alone.