Code point
U+3351
Glyph appearance depends on your fonts.
U+3351
So<square> 30EA 30C3 30C8 30EBU+3351 SQUARE RITTORU is a Unicode 16.0.0 character in the Other Symbol category. It belongs to the CJK Compatibility block.
Choose the representation you need, then copy its value.
U+3351
13137
㍑
㍑
E3 8D 91
3351
00003351
%E3%8D%91
\u3351
\u3351
\u3351
\3351