Asriel is a young boy no older than 12-13, so his voice should still be a higher pitch. Asriel example: https://youtu.be/1CNw5n0MIHo

Asriel is still getting used to having emotions again after being Flowey for so long. And to avoid ruining the happy ending everyone was finally able to achieve, he tends to keep to himself and bottles everything up.

He also tends to tear quite easily, so the VA should be able to convey said emotions. He also gets into some fights, so be prepared to do grunting/screaming should you get the role.

Role: Asriel is a main character and has major roles in all three episodes.