Complex sentence: As Shido successfully keeps sealing more and more Spirits, he gains allies to help him with his dates with other spirits, but also increases the competition among them for his attention and affection, much to his chagrin.
Split into simpler sentences: As Shido successfully keeps sealing more and more Spirits, he gains allies to help him with his dates with other spirits. Shido also increases the competition among them for his attention and affection, much to his chagrin.