Yeah, no, thanks. Love isn't a cheap item that could be given to just anyone. It's reserved for only one special person where you stay loyal to them regardless of their presence.
The ability to love multiple people in your lifetime does not make your love be worth any less. Love is a virtue, and a blessing. Regardless of how *you* may personally experience it (which will always be valid) that does not diminish the loyalty of others and the intensity of what they feel. Love, just like any other emotion, is not defined by a single iteration and possibly; you quite literally cannot feel what someone else feels or does not feel, so, it's genuinely impossible to analyze it in a way so as to label it "cheap." No matter how well someone explains it, or how well you may think you understand it, you will never have the actual experience. You can also never actually interfere in what someone feels; so people (be it in this story or irl) will continue to fall in love multiple times in their lifetime, even if to you that shouldn't be possible.
To think Ukai's loyalty falters by him simply loving someone else years after Amakata's death is also a huge disservice to the meaning of the word. Ukai loving someone else does not mean he has stopped cherishing Amakata's memory, or that he no longers love him, or that Amakata is no longer important to him. Amakata will always be a huge presence to Ukai, just in a new/different way – and I am more than sure that his memory is better cherished when Ukai allows himself to be happy and to love, than if Ukai closed off his heart simply because of Amakata's memory. It was already hard for Ukai to find love again; there is no reason to question his "loyalty" here.
So, to sum it up, simply remember everyone is different and there is no reason for you to belittle the weight of someone's feelings simply because they do not match your own, personal experience/view
Ukai is so, so loved... I'm genuinely so happy to see it. This isn't a story about fighting jealousy or whatnot, it's just a story about a man who had two lovely people who couldn't help but think of him as lovely as well. I get so wobbly with the way they *both* portray loving Ukai as loving his passion, too, and supporting it so wholeheartedly and genuinely... <3 <3 may this kind of love find us all!!!