Complex sentence: Shori adopts Celia and Brook as her own symbionts to save their lives, though their bonding is initially uncomfortable for all of them as symbionts become addicted to the venom of one particular Ina.
Split into simpler sentences: Shori adopts Celia and Brook as her own symbionts to save their lives. Their bonding is initially uncomfortable for all of them, however, as symbionts become addicted to the venom of one particular Ina.