noun
must-buy; must-have item
A product or item that is highly recommended for purchase, often used in marketing, reviews, or travel recommendations.
この化粧水は本当にマストバイだよ。
This lotion is really a must-buy.
旅行のお土産でマストバイなのは、このチョコレートです。
The must-buy souvenir from the trip is this chocolate.