A 4 Fr child catheter (KIWAMI ST01; Terumo Corp., Tokyo, Japan) can be used in combination with a conventional 6 Fr mother guiding catheter to deliver stents into complex coronary lesions without difficulties1. Four Fr child catheters can be inserted into 6 Fr or 7 Fr guiding catheters with a second guidewire for side-branch protection. In this report, we introduce a new technique for delivering stents into complex bifurcation lesions with side-branch protection.