Complex sentence: After Matsuri and Kagetora die in the old future, he becomes extremely upset and he dies after over-using his powers in order to save 30 people who should have died from their wounds.
Split into simpler sentences: After Matsuri and Kagetora die in the old future, he becomes extremely upset. In the old future, he dies after over-using his powers after saving 30 people who should have died from their wounds.