Ritsuko is a kind and responsible girl.
Ritsuko is a young girl that stands on 165 cm (5'4") and weights at 54 kg (119 lbs). She has to shoulders length dark brown straight hair that she wears in pigtails. Ritsuko's eyes are brown.
A childhood friend of Sentarou and daughter of records shop owner Tsutomu Mukae, Ritsuko is a representative of class, to which Kaoru and Sentarou are belonging. As well as Sentarou, Ritsuko is a Roman Catholic and attends church together with him.
She is also Kaoru Nishimi’s wife (thus making her Ritsuko Nishimi) & eventually becomes pregnant with his child at the end of the manga.