An assembly includes: an attachment; and a container. The container includes a main body and a tube section, the main body forming a storage space, the tube section having an opening that communicates with the storage space, the tube section having an outer circumference surface provided with a first engagement section, the first engagement section having a first surface facing a first direction that is a direction toward the storage space. The attachment includes a ring-shaped section that is fittable with the tube section, the ring-shaped section having an inner circumference surface provided with a second engagement section, the second engagement section having a first surface facing a second direction away from the storage space, the first engagement section and the second engagement section being engageable with each other when the first surface of the first engagement section abuts the first surface of the second engagement section.