Complex sentence: In the end, after seeing Mao's sad and tearful face, realizing his true feelings for Mao and her feelings for him, Souma decides to give up his chance of going back to his own world and decides to stay with Mao and Weissritter.
Split into simpler sentences: In the end, after seeing Mao's sad and tearful face, he realizes his true feelings for Mao and her feelings for him. Souma then decides to give up his chance of going back to his own world and decides to stay with Mao and Weissritter.