君次第だ

it's up to you

→ 君
phrase Uncommon #16,440
it's up to you 君次第 means that the outcome or decision depends on you. 君 is a familiar, informal way to say “you.”
JA: どこで食べるかは君次第だ。
EN: Where we eat is up to you.

行くべきかどうかを決めるのは君次第だ。

It's up to you to decide whether to go.

君次第だよ。

It’s up to you.

それはまったく君次第だよ。

That’s entirely up to you.

君の将来は君次第だ。

Your future is up to you.

成功するかどうかは君次第だ。

Whether you succeed or not is up to you.

勉強するもしないも君次第だ。

Whether you study or not is up to you.

我々が成功できるかどうかは君次第だ。

Whether we can succeed depends on you.

決めるのは君次第だ。

It's up to you to decide.

君次第だ!

It's up to you!

— ピエロがお前を嘲笑う (2014)

我々が生き残るチャンスは…君次第だ、ザッチ君。

Our chance of survival... depends on you, Zatch.

— アトランティス 失われた帝国 (2001)

選択は全く君次第だ。

It's entirely up to you.

試験に受かるかどうかは君次第だ。

Whether you pass the exam is up to you.