User blog comment:B214/Shin DxD 1 discussion/@comment-34061653-20180926000306/@comment-24595619-20180926170933

There are varying species of Youkai, I'm just saying that all of them aren't weak against light. Like Kunou is a Kyuubi (Nine-Tailed Fox). And none of the other species of Youkai that appeared in High School DxD have been shown to be weak against light unless you can't Koneko and Kuroka who're reincarnated Devils.

There is also a number of ways that this can be interrupted.

“Ah, I have not thought that far ahead…… Hmm, although I can hold them with no problem…… Thinking back, there are only a few from my kind who can use these tools as well.”

Like there is a specific group in Kyoto who's allowed to use them as tools or even capable of using them as Konou never mentioned that other species of Youkai will be injured if they touch them.