These are message cards made by mocolier, a Japanese manufacturer of stationery and paper goods.
The card that you will want to gently add to a simple gift.
The illustration of the flowers is not too cute and blooms casually.

The following is a quote from mocolier's product description
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This card set comes with a case containing six each of pink flower, blue flower, and yellow flower message cards.
The cards feature designs of flowers used in flower arrangements and bouquets, such as poppies, marguerites, and mimosas, on both sides, and are based on subdued colors, so they are not too flashy and can be used for a variety of occasions.
It is recommended for everyday messages, business occasions, and when you want to add a few words to a gift.
The card is made of high quality paper with a texture that is easy to write on, without the worry of backing.

Size: 5.5 cm (length) x 9.1 cm (width) (business card size)
Material: Paper, leather strap
Contents: There are 18 sheets in total.