SDCL § 55-1-13: Voluntary trustee--Assumption of relationship.

Everyone who voluntarily assumes a relation of personal confidence with another is deemed a trustee within the meaning of this chapter and chapter 55-2 not only as to the person who reposes such confidence, but also as to all persons of whose affairs he thus acquires information which was given to such person in the like confidence or over whose affairs he, by such confidence, obtains any control.