The battle with Kai reveals secrets that the Nagatsukis would rather leave unknown.
him learning it all in a 
short time and then leaving.
من معرفته دُفعة واحدة خلال
فترة قصيرة ثمّ المُغادرة
avrei più occasioni.
do que aprender tudo de uma vez.
а не выучится быстренько
 и уйдёт с концами.