hontī could be both singular and plural in accusative case. The adjective sȳri is in plural form. That's the only way to know that hontī is plural.
Wait so, is kēla plural? I thought it was lunar, which would make it kēli in its plural form. Not only that, but the Duolingo's High Valyrian dictionary cites "cat", singular, as kēlys, and plural as kēlas. Am I missing something?