Dutch writer Marie Anderson corresponded with Busch. More than fifty letters were exchanged between January and October 1875 in which they discussed philosophy, religion, and ethics. Although only one Anderson letter survives, Busch's letters are in manuscripts. They met in Mainz in October 1875, after which he returned to Basserman at Heidelback in a "horrible mood". According to several people at the time, Busch's failure to find a wife was responsible for his conspicuous behaviour. There is no evidence that Busch had a close relationship with any woman after that with Anderson.