Liquid Supply Set, Liquid Supply Apparatus, and Liquid Ejection System

Provided is an ink supply set configured to detach from a liquid supply apparatus and includes an ink containing portion, a connection unit, an ink guiding portion having an engaging portion, a flow path unit that guides the ink in the ink containing portion to the ink guiding portion, a circuit board, and a substrate installation portion. The liquid supply apparatus includes a liquid introduction portion into which ink is introduced via the ink guiding portion, and a movable support portion that supports the connection unit. In a state in which the engaging portion is engaged with a first engaged portion formed in the movable support portion, the circuit board comes into contact with an electrical connection portion provided in the liquid supply apparatus, and in the removed position, the circuit board is separated from the electrical connection portion.