In a 58-year-old man with HCC undergoing TACE, a segment III tumor was supplied by an accessory left hepatic artery arising from the left gastric artery (LGA). The dominant technical challenge shifted from acute angulation at the LGA origin to inadequate back support in distal branches. To overcome repeated dislodgement, the catheter was exchanged for a 5-Fr catheter with a hand-cut side hole, positioned at the LGA orifice while the tip was anchored in the celiac trunk. This technique allowed a microcatheter to traverse in a single well-supported pass, enabling successful superselective TACE without immediate complications. This case emphasizes the importance of distinguishing ostial angulation from back-support failure and highlights the utility of proximal side-hole anchoring in complex multivessel selection.