expression, ichidan verb
it's obvious that; it's bound to be; surely
Expresses strong conviction that something is naturally or inevitably the case. Often used in casual conversation. The speaker is certain about the outcome or state.
そんなことを言ったら、彼女が怒るに決まっている。
If you say something like that, she's bound to get angry.
毎日
If you practice every day, you'll surely get better.