The letter and vow to his homosexual partner, Gensuke KASUGA (later Masanobu KOSAKA) whom Shingen loved, in which Shingen stated his excuse for his love affairs ((1546) they are currently possessed by the Historiographical Institute of The University of Tokyo, complete with a vow to Harunobu TAKEDA), still exist.
また、信玄が寵愛する衆道相手の春日源介（後の高坂昌信）に対して、浮気の弁明を記す手紙や誓詞（天文15年（1546年））武田晴信誓詞、ともに東京大学資料編纂所所蔵）が現存している。