Japan: What are these? Possibly First Day Postmarks?

Picked up some lots I won at the last Rasdale Auction today and found a stamp album with these inside. They look like Japanese First Day Postmarks to me. Has anyone ever seen anything like this?

Applications for the Commemorative Coin for Expo 2025 Osaka, Kansai, Japan ( First Issue) Begins August 8!

Japan: What are these? Possibly First Day Postmarks?

Japan plans huge domestic postal rate increase for 2024

First Day Of Issue: Most Up-to-Date Encyclopedia, News & Reviews

Schuyler J. Rumsey Philatelic Auctions Sale - 108 Page 78

Kansai Thru Pass

Daniel F. Kelleher Auctions, LLC Sale - 790 Page 11

Japan commemorative postmark, inter-highschool championships, baseball, (jc3589)

Japanese vintage historical Post Card with Japanese characters, pink red patterned frame, Imprinted stamp, National emblem, postmark, Japan Empire Stock Photo - Alamy

First day of issue - Wikipedia

Just found out about pictorial postmarks! : r/RAoC_meta

Postal history hi-res stock photography and images - Page 3 - Alamy