に違いありません

must be

→ に
phrase Rare #32,296
must be A polite expression of strong certainty or deduction, meaning that something is almost certainly true. Often follows the plain form of a verb, adjective, or noun.
JA: 彼はもう家に帰ったに違いありません。
EN: He must have gone home already.

彼はゆうべ飲みすぎたに違いありません

He must have drunk too much last night.

ここにはあなたの心を掴む魔法があるに違いありません

There must be some magic here that captures your heart.

— ウィキッド 永遠の約束 (2025)