A Green Magic by Alix Hadden

Kir doesn’t want a relationship. Nor does he want to be dealing with magical attacks. Seems like he’s in trouble on both counts.
Mage Kir Davies has sworn off romance — until he runs into Zach Kassel at his local climbing wall. But when dangerous magical emanations are showing up across his patch of London, getting involved with a non-mage is surely just too risky.
Zach will admit that he was a little surprised to be attacked by semi-sentient mud on a first date, but for Kir, he’s prepared to get over it. And to do his best to help — except for the bit where Kir seems to think that he’s personally responsible for looking after everything and everyone all by himself. That’s more than a little annoying.
As the magical attacks get worse, Kir must find out what’s happening, and learn to accept help from those around him — before whatever is rising underground takes out him, Zach, and half of London.