After some deliberation, I came up with a song for his theme. This song fits both Emil at the start of his journey, and toward the end, when he develops an identity crisis about the dark and light in himself. It sounds more like an letter from Marta (his love interest) to him, IMO. Since she's so open and supportive from the beginning, it makes sense.
love is all the good in you
love is peace when peace is fragile
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