Yoosung is a really nice and lovable person, and is described by the other RFA members as 'a real puppy'. Yoosung cares about others a lot and loves to spend time with others. He is naive and believes things that are told to him more often than not, as shown during several of his interactions with 707. As a result, he is often unforgiving to his naive nature.

Because of the sadness in his heart from Rika's death, he often talks with the others about her and compares her with the player, even though he is fully aware that the player and Rika are not the same person (not counting Bad Relationship Ending 1 where he confuses the player as Rika). Yoosung is also often jealous of other people like Zen for his good looks or Jumin Han for his rich and different life.

He is also possibly known to get very possessive, as you go along in his route, during one of his calls he clearly states "I don't want you to look at anyone but me", possibly signalling that he wants the player to see only him as her significant other. - MM wiki.

What I'm looking for is:

Of the dateable characters he falls into the cutesy character, that people feel they must protect the innocent little cinnamon bun.

Twenty-something-  Medium/Medium - Cheery/more naive sounding voice.