Thats not really bad, just tragic. A bad "yuri" ending would be the boy from the flashback joining their office to get revenge. He manipulates them and makes Kisaki think he and Chishiro are in a relationship. This causes her to fully transform into a tree and he abuses Chishiros sorrow to actually start dating her. After geting married and buying a house they arrange for the tree to be moved to their garden. Except he swaps it with another and makes a bed out of the real Kisaki. They make lots of babies on the bed. 10/10, depressing as fuck, [everyone hated that].