When Hachi gets jealous while Misato visits the two for the first time, Hachi says to Nana that she's selfish. Nana reacts shocked as if this happened before. Is there a reason why she reacted this way?

In the original Tenchi Muyo OVA, the lead character - Tenchi Masaki - strikes down the franchise's first villain Kagato in a sword duel. As Kagato dies he says the following phrase: 天智,マスターキーと同じか. 津波目. これでわ再生もきかんか? 素晴らしい 私の負けだ、少年 Which loosely translates to: Tenchi,the same (name) as the maste...