The Chicken Katsu Sando - Breast (胸肉チキンカツサンド) is chicken katsu specifically using breast meat; lean, tender.
It sits within the Japanese Sandos family of French sandwiches — specifically the The Katsu Sando cluster, which gathers the regional and stylistic variants that share its frame.
For the broader The Katsu Sando tradition that frames this sandwich, see The Katsu Sando.