Although, he is always insulting Domon and auguring with him. The two men eventually became un-admitted friends, after Domon came to the conclusion that Ayase was simply over-sensitive and so his odd, defeatist attitude was generally ignored by Domon. They sometimes share a common hostility towards things. Ayase and Yuuri are seemingly similar as they are both calm, followed one path to recapture the Londarz clan and are both the voices of reason amidst the other three. In Episode 9, Tatsuya calls them to make a toast, but Ayase looses control of wine glass and it falls. He clutches his heart and struggles to walk, Tatsuya is the only one to be truly worried. In the next episode, Ayase reveals to him he had a physical checkup and found out he has an incurable terminal illness called the Osiris Syndrome. Once the symptoms show, there's only a year or two left. He did not tell his parents, nor his friends. He fought because he didn't care he would die, but one day he realized he really did want to live. He considered helping others not much of a self-sacrifice.

Tatsuya was the only one that kept the secret until Episode 39. Domon and Yuuri determine they must send Ayase back to the 30th Century. Tatsuya sticks by his friend, saying he hasn't given up and that is why he is still a Timeranger. In Episode 14, it was revealed that back when he was still racing, he had a competitor he was in friendly terms with, called Baron. After one race, Baron killed a pedestrian because of reckless driving. Ayase stood witness and captured him, but knew he was not evil for all that. He has a soft spot for children. At one point, Honami had a crush on Time Yellow and believed Ayase was him. She was completely different from his type, but was she was not the type he hated. Ayase was surprised when Domon asked him to meet Honami, even though he knew Domon had a thing for her. Despite his best efforts to provoke Domon into changing his mind, Ayase eventually allowed himself to be talked into it. Ayase had no interest in having a relationship with her and every interest in helping Domon get together with her. For he knew how lonely Domon was.

Ayase had what seemed to be an instinctive understanding of how Naoto operated. He fully expected Naoto to behave coldly, but it was Ayase who went to Naoto for help in getting the money to pay Dorunero for the vaccine to save people from a killer virus. Ayase, who is the only Timeranger that has a driver's license, works as an escort at Tomorrow Research. On his license, his name is Ayase Shinnosuke and his birthdate was February 18, 1978. Ayase had been dying for so long, that he was rather used to it. Therefore, when the Timerangers were told they could return where they belonged, he was the least concerned about it. When Domon asked him what they should do if they can figure out why the Earth would be destroyed in the year 2001, he said that for himself he would fight to stop it. He has lived in this time so long, the other has become something of a dream to him. Unreal, and therefore not as important as this moment. For Ayase lives in the moment. Even when he was offered his life, that idea was another thing too unreal for him to be bothered with. All that mattered was saving Tatsuya and his time from certain destruction. After time was altered at the end of the series, a cure for Osiris Syndrome was found and Ayase was cured.