The JST 03R-WPJV-3-EMM(N) is a 3-position receptacle from the WPJ series, a wire-to-board interconnect family built for environments where moisture ingress is a real concern. The housing carries a JIS C 0920 Grade Level 7 rating — that's the Japanese equivalent of IP67-level protection when mated with the matching plug, meaning it keeps out dust and handles temporary submersion.
This is a bare housing — contacts are not included. Free-hanging (in-line) mounting means it sits on the wire harness, not on the board. The blue colour is a visual key for the WPJ family on the line.