Japanese Naval Signal Flag #3—Code "San" 最初の3の日本の海軍艦隊信号-名前「さん」

The Japanese number 3 three is basically an echo of the Kanji - Chinese Character - for the number three.  The Kanji for three consists of three horizontal stripes.

Japanese Naval Signal Flag #2—Code "Futa" 最初の2の日本の海軍艦隊信号-名前「ふた」

The Japanese Naval signal flag for the number 2 is called Futa ふた.  The design of the flag has a blue field with two yellow rectangles along in the middle of the flag near the fly and hoist.

 The unique Japanese auxiliary number flags were used with international maritime flags.  Recently in an Anime series about female sailors, the Aux #2 flag has appeared leading with X-Ray and India for a code of 2XI.

Japanese Naval Signal Flag #1—Code "Hito" 最初の1の日本の海軍艦隊信号-名前「ひと」

There are several types of maritime flags to represent the number one.  Most famously the International Maritime standard uses a flag that looks like the national flag of Japan.  However it is a pennant and the red disc is off center towards the hoist.

NATO has number one flag that looks like the of Spain; because it is a horizontal tribar of red, yellow, red.  Thus its nickname is 'UNO'.

Russia oddly uses the International Maritime flag in a different way for its numbers.  The Alpha flag is the number one flag for Russian allied fleets.  Luckily Alpha is also the first letter of the alphabet, so it makes sense.

But the Japanese Navy has created unique flags.  Their flags have an International Maritime feel, but they are unique to Japan.

The Number 1 flag of Japanese Naval forces has a white background with blue diagonal stripe from the lower hoist to the upper fly (a dexter bend).  In a what the Japanese flag is very effective since the single blue line is a unique flag even among national flags and reflects the single line of one, as it is used in Western and Chinese symbols.  The Indo-Arabic-Western number for one in a single vertical line, while the Eastern symbol for one is single horizontal line.

Japanese Naval Signal Flag #0—Code "Rei" 最初の0の日本の海軍艦隊信号-名前「れい」

The Japanese Maritime Zero Flag uses the colours blue and white.  It has the pattern of the Zulu flag but in the hoist and fly triangles is blue, while on the chief and compartment triangles it is white.

The Japanese Auxiliary Zero Flag make intuitive sense, more so than the International Maritime Flag.  Firstly, the empty hourglass shape indicates that time is up—it has reached the zero hour.  You can imagine that the blue triangles on the hoist and fly are ocean or sky.  Likewise Zero Flag follows the shape-pattern of the Zulu flag.  Thus Zero and Zulu combine for a unique flag.

 You can see the Zulu and Zero flag with Lima in the first upper left hand column.  On the right page you can see the codes that all begin with Rei.

数の日本の自衛隊海軍旗 - Japanese Naval Flags for Numbers 0 to 9

Flag being represented by numbers is common property of modern navies.  Famously there is the International Maritime Code, but several nations have their own kinds of flags for numbers.  NATO has them, as does Russia, and so do the Japanese.

Here are the unique flags of Japanese Navies that utilize unique designs for the numbers 0 to 9.

You can still purchase these unique Japanese Number flags with model kits.  Note the Movement flags have been deleted in this image.  The flags are like stickers that fold up on the miniature flag poles.

SOURCE
http://dreadnoughtproject.org/friends/dickson/Complete_Signal_Book_version_2.pdf

Japanese π Flag - Using Japanese Signal Flags for 3.14

The Fun Japanese π Flag is based upon the unique maritime signals flags of the Japanese Naval Self Defense Forces.  In this case the flag for 3 is the main component, the flag for 1is the blue diagnoal with white fimbration, and finally the flag for 4 is the circle with four blue dots.

This flag is for fans of Japanese culture and who love math, especially that enchanting number of pi: 3.14.

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Better Version 2.0 added August 18, 2021 --令和三

No Man's Land Flag - Conquering the Furies of Internet

 Flags in video games are nothing new.  The story of the Hero's journey is behind the making of this game.  Upon the release, it failed miserably.  However the game developers did not surrender.  Eventually a fix was released called Foundation Update and it featured flags flying. The flags are long rectangular fields with blue, white and red patterns. 

The story of No Man's Land is a true story from hyped hero to zero back to a true hero.  The Internet Historian can better explain...

Basically the programmers at Hello Games perilously summoned the Vengeful Furies of the Internet.  However they would eventually overcome.  It was with grit, patience, self-reflection,  that they were able to calm the savage nature of the Internet.  It is the modern tale of the ultimate come back, with grace, the rise of the Phoenix.