This item was on the 01-2016 LoAR
28: Samukawa Mantarou Yukimura - New Device
OSCAR finds the name on the Atlantia LoI of October 31, 2015 as submitted.
Argent, three tomoe in annulo azure
O-umajirushi: A 17th-Century Compendium of Samurai Heraldry translated and annotated by Xavid "Kiho" Pretzer p. 91 says "The motif has been used since at least the 11th century."
The tomoe is a period Japanese charge, generally used in threes. Attached are a few period banner designs including mon of three tomoe. The first three are from /O-umajirushi/, published in Japan by 1644. The last one, three tomoe in a square enclosure, is from /Kenmon Shokamon/, published in Japan around 1470.
This documentation was used in a badge submission for Miura no Matatarou Koreyoshi.
There is a step from period practice for use of Non-European charge.
The above submission has images. To view them, see the URLs below: