[2] Kupenov made his unofficial debut for the first team of Botev Plovdiv on 15 November 2014.
[3] On 23 May Kupenov was included in the squad for the 1-2 away defeat from Beroe Stara Zagora but remained an unused substitute.
[7] In August 2016 Kupenov joined Septemvri Sofia officially on a loan deal until January 2017.
[9] Sadly, on 9 February 2017 it was reported that he will probably miss the remainder of the season after sustaining an injury.
[13][14][15] In March 2016 Kupenov was in the starting lineup of Bulgaria U19 for the 0-1 defeats from Belgium U19 and Croatia U19.