Yōsuke is a friendly young man being one of the most sociable and kind people in Class 1-D. His kind nature has allowed him to be elected as the one of the class representatives.
Class D Edit
Yōsuke seems to have close a relationship with Kei as when school first started, she cheered on his idea of the class introducing themselves. After several days of school, they seem to have become a couple or at least formed a bond as they are often seen together.
In truth, they're just pretending to be in a relationship so that Kei would not get bullied in school so it is unknown how they really feel about each other. However, it shown he does care for her as when Kei's underwear is stolen, Yōsuke searches the boys for them though he covers for Kiyotaka after finding them on him; he asks for the panties as he will suffer less being Kei's "boyfriend".
In return, she seems to trust him as she selected him to be part of the guards for the boys after the girls demanded the boys being separated from the girls. This was seen again as she defended him when Suzune hinted that he could possibly do mischievous activities while acting as a guard. However, she did see Suzune's point and went along with the latter's decision to make Kiyotaka a guard as well to keep an eye on Yōsuke.
In the light novel of Volume 4, despite being promised to protect Karuizawa from being bullied by Manabe and her group, Yōsuke doesn't want to take a side and want to discuss it peacefully without using violence against someone. He did offer his help to her, but since he's not her real boyfriend, he didn't need to go that far for her. He also tells her that he won't help her like this and she won't be able to depend on him if there's nothing he can do for her.
Yōsuke is one of the few people in Class D to have any interaction with Kiyotaka.
They first met when Class D started to introduce themselves and Yōsuke applauded him for at least trying to make a good impression after he messed up somewhat.
In the months after this, they barely interact but during the cruise Yōsuke tries to get Kiyotaka to help him get Suzune to open up and get him to socialize with the rest of the class.
During the survival test, he and Kiyotaka work together in getting things ready for the camp. When Karuizawa's underwear is stolen, Hirata searches the boys for them and though he finds them on Kiyotaka (after Ike placed them on him) he covers for him, to the latter's surprise. Kiyotaka soon questioned him on covering for him as Yōsuke reveals he knows that Kiyotaka wouldn't do such a thing. This implies he trusts him to a degree, despite barely knowing him. When the girls put Yōsuke on guard duty, Suzune had nominated Kiyotaka as another guard to keep watch on him. This decision was accepted by Yōsuke who tried to lift the spirits of Kiyotaka after he complained about being a last resort.
Before the test ended, Kiyotaka gave Hirata the news of Ibuki and Suzune as he sunk into despair at the class failing. Ayanokōji soon asked for a favor which was to make him the leader and told Yōsuke the other class leaders while giving Suzune credit. His actions allowed the class to succeed and relieved Hirata who had no idea of Ayanokōji's role.
Unknown to him, Kiyotaka reveals that he doesn't acknowledge him as an ally, but merely just a pawn for him to win.
In the light novels, it appears Yōsuke has caught on to some Kiyotaka's actions which have helped their class proceed. Its unknown what his reaction is to this but he may not hold against Kiyotaka since he is helping out the class.