The BtoC-EC market size in Japan in 2018 has reached 18 trillion yen, and has been continuing to grow in recent years. Coupon distribution is one of acquiring and maintaining methods of customers in EC market. In this study, we analyzed the purchase behavior using ID-POS data of a golf EC site using cause and effect analysis. Especially, we focused on the behavior of the second purchase because when customer used a coupon in the second purchase, the life-time value of the customer seems to increase. From the result of analysis, we focused on consumer growth of the future, and discuss the utilization of coupon in the EC site.