でいようね

let's stay

→ だ
phrase Rare #36,738
let's stay A friendly, reassuring way to suggest continuing to be in a certain state or relationship, such as being friends. でいよう is the volitional form of でいる, and ね seeks agreement or warmth.
JA: いつまでも友達でいようね。
EN: Let's always be friends.

ずっと親友でいようね

Let’s always be best friends.

ずっと友達でいようね

Let's stay friends forever.

いつまでも友達でいようね

Let's stay friends forever.