Complex sentence: When Itsuki uses his Glam Sight his personality becomes more dominant and his confidence is boosted;, but when the Glam Sight is sealed by the eye-patch he reverts back to his original tender personality.
Split into simpler sentences: When Itsuki uses his Glam Sight, then his personality becomes more dominant, and his confidence is boosted. However, when the Glam Sight is sealed by the eye-patch, then he reverts back to his original tender personality.