Complex sentence: Kotetsu keeps a journal to track his decreasing power, each entry showing a decrease of two to five seconds per use.He dies in the episode 24 in order to save the rest of his friends from being killed, sacrificing his own life.
Split into simpler sentences: Kotetsu keeps a journal to track his decreasing power, each entry showing a decrease of two to five seconds per use. It is speculated that he dies in the episode 24 in order to save the rest of his friends from being killed, thus sacrificing his own life.