Wedding anniversary years have well-established connections now common to most nations: 5th Wood, 10th Tin, 15th Crystal, 20th China, 25th Silver, 30th Pearl, 35th Jade, 40th Ruby, 45th Sapphire, 50th Gold, 60th Diamond, and 70th Platinum. In English speaking countries the first, wooden, gift was cut on the day of celebration and then presented to the wife as a finished article before the next two quarter days had passed. The modern tradition may have originated in medieval Germany where, if a married couple lived to celebrate the 25th anniversary of their wedding, the wife was presented by her friends and neighbours with
Lead 15th Anniversary Live Box MCs. For "Lead 15th Anniversary Live ～Kan Ima Shirube-sai～", the group performed every a-side they had released since their debut in 2002, up until their then-most recent song "Beautiful Day", which had been released on August 23, 2017. The live was well-received, with people praising the group's stage presence and charisma, even with performing so many songs for one performance, many of which were dance tracks. "Lead Upturn 2017 ～This is Our Day～" was the group's fifteenth live tour. For the performance, most of the music utilized were songs from their seventh studio album "The Showcase", which had been released