It's neither letter paper nor a small envelope, but a small patterned pouch (flat bag) with a flap that can be used for small errands.
It can be used for a variety of purposes, such as wrapping gifts, small gifts such as sweets and accessories, and dividing small items.
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Size: Length (unsealed) 182 / (sealed) 168 x width 115 mm
Paper type: One-sided glossy kraft paper
Printing: Print on demand
Origin: Japan
Number of pieces: 4 (2 isopods/2 octopus pieces)
*Please be careful when putting heavy or sharp objects in the bag as it may tear.