Complex sentence: In the end however, Gennosuke tricked Tenzen into overextending himself which granted Gennosuke the opportunity to decapitate him with his sword before he called out for Oboro to take up Tenzen's blade so they could finally bring an end to the ninja war.
Split into simpler sentences: In the end however, Gennosuke tricked Tenzen into overextending himself which granted Gennosuke the opportunity to decapitate him with his sword. With their mutual enemy dead, Gennosuke called out for Oboro to take up Tenzen's sword so they could finally bring an end to the ninja war.