くてはいけない
nakutewa ikenai

Expression

1. cannot do without something; indispensable; absolutely necessary

Usually Written in Kana
きみはもう大人 おとななんだから、もっと分別 ぶんべつがなくてはいけない。
kimiwa mō otonana ndakara motto fumbetsuga nakutewa ikenai.
Now that you are grown-up, you ought to know better.
Expression

2. have to do

Usually Written in Kana