Some TMNT stuff really isn't for little kids.
Hayashi Toru was a yakuza boss working in Tōkyō, Japan. Toru had heard of Oroku Karai before his granddaughter Natsu brought news that she had fought with her, after incidentally shooting Karai in the shoulder during a yakuza hit.
When Karai appeared on his balcony to kill Natsu, Toru asked her to delay whatever vengeance she had in mind while he enlisted her to find something for him: a legendary sword whose historical origins might make his enemies think it was magic. Intrigued by the idea, Karai agreed.
However, Toru had purely practical reasons for sending Karai on this quest: he had decided she was an unacceptable threat, as evidenced by her intrusion on his property and threat to Natsu. As a result, he had a team of assassins waiting to ambush her when she emerged from the cave where the sword was located. Natsu was horrified by her grandfather's actions, deeming them dishonorable, but Toru dismissed the idea, believing that the death of Natsu's parents—Toru's daughter and son-in-law—had come about because of a sense of honor.
His plan was derailed by Natsu warning Toshiro of what was happening, allowing the sensei to dispose of the assassins before they could harm Karai. Karai then invaded Toru's compound with the magical sword, where she decapitated him inside his safe room. She then took over his businesses.