Feb 26th, 2017: A few months before the group concert, Xiao Zhan said that he wanted to sing this song to his fans.
But during said concert in April 2017, he did not have any solo time.
Four months later, in the weekly vlog of June 26th of 2017, he mentioned this song again, saying that the lyrics make him think of his fans.
October 2018: a year and four months later, during the second concert, he still couldn't sing it.
December 2018: a year and six months later, during the third concert, he could not sing it again.
At last, in June 2019, two years after mentioning this song for the second time, he sang it acapella in Cosmo Fashion's digital magazine.
On July 12th 2019, during The Untamed fanmeet, he sang Kepler live for the fans.
Why Kepler: Stephanie Sun, the songwriter, explained that Kepler is the name of a supernova, it has existed from the 16th century till now, it's the first star capable of being seen by naked eye during the day. At that time, this star shone for 3 weeks during daytime.
In the lyrics, it's mentioned that one can find you even in the middle of other stars, this sort of feeling given to me, makes me hope that I can offer the same feeling back to all her fans.
Stephanie Sun compared her fans to be stars who gave her an incredible amount of light, and made her into the supernova that shone as the brightest star in the night sky.
Xiao Zhan, who is one of Stephanie Sun's biggest fans, adopted the same view of his fans, and this song became a very significant song in the fandom naturally.