At his grandfather's funeral, Daikichi Kawachi stumbles upon a lone young girl, Rin Kaga, in the garden. Surprisingly, she is rumored to be his grandfather's illegitimate daughter. With the family unwilling to embrace her due to the scandal, Daikichi steps up, deciding to raise Rin on his own despite his inexperience and single status. Usagi Drop tracks their journey as they navigate newfound responsibilities and seek meaning in their unexpected bond.