Complex sentence: To make sure that the other children did not repeat this, he took drastic measures to keep them from ever disobeying him, especially Makoto, his only son who would be heir to the dojo.
Split into simpler sentences: To make sure that the other children did not repeat this, he took drastic measures to keep them from ever disobeying him. Especially Makoto, his only son who would be heir to the dojo.