Kaede thinks Tenko is cute, spending a good deal of time complimenting her appearance during Free Times Events, which greatly embarrasses Tenko, surprising her and causing her to blush. Due to her prejudice against boys, Tenko warns Kaede about Shuichi, even though there is no real reason for it. Since Kaede is a girl, Tenko is willing to protect her from degenerate males.
When asked by Kaede why she adores Himiko so much, Tenko blushes heavily, and confesses to the pianist that she admires performers. She tells Kaede of her dream to be a cute magical girl, but says she can't do magic, and she's not cute. Kaede, of course, tells Tenko she thinks she's cute, which flusters Tenko further. Kaede proceeds to compliment her smile, passion and body, which Tenko either refuses, or blushes at.
Nonetheless, Tenko seems to really like Kaede, and is heavily protective of her during the first trial.
Tenko didn't believe that Kaede is the one who killed Rantaro, even went far in risked her own life to prevent her from being executed along with Kaito and Gonta. After Kaede requested her and the others to stop, she witnessed the execution and started crying afterward.
This ship sailed as a result of the few interactions between Tenko and Kaede. It may have also been because of Tenko's positive views towards most of the female characters, and her being shown to be able to have romantic feelings regardless of gender.
There are also several canon scenes between the two that also fueled this ship, such as Tenko refusing to believe Kaede was the culprit of trial 1, Tenko fighting against the exisals alongside Kaito and Gonta to prevent Kaede's execution.
This ship also gained attention due to being canon or heavily implied to be canon in several popular fanfictions, most notably "I'd trade my life for yours" by Grayimperia.