Post History
Any character present throughout the story should have some sort of good reason to be there, especially a character like you describe that will clearly be risking their life and conscience in escal...
Answer
#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/31893 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/31893 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
Any character present throughout the story should have some sort of good reason to be there, especially a character like you describe that will clearly be risking their life and conscience in escalating battle and wrong-doing. Why don't they quit? What do they stand to gain that is so important to them? At some point, it becomes implausible to continue saying "they just want treasure". I'd expand on your young man. Ditch the "secret admirer" aspect, ditch his shyness or innocence, even give him a previous girlfriend. Have him declare his love. Your MC pretends he is not serious, and she is naive, and just wants to be friends. He is heartbroke, but your demigod promises him if he does not go on the quest, he will never gain his heart's desire. THAT'S why he goes, he thinks it is the only way. Then after he risks his life to save the MC, gets injured and brought back to health by her, then he does it AGAIN, and she eventually realizes she is in love with him and tells him so. Consummated love is a powerful reason for him to stay by her side until the bitter end, and that is his story arc, from rejected suitor to beloved mate. It can end in happily ever after, or his death to save the MC, either way. I think you have to give him some depth, if he is going to be present throughout the story, just for plausibility.