Honestly I'm cool with Kaichi using Golden Hour once or twice at the peak of super-hard battles. As far as cheat skills go, it's not really giving him an extra advantage he never had, it's basically letting him access his own peak power levels. Ultimately it would still be his own strength, and I can see it leading to some epic climactic battle moments. His own pride as a martial artist would act as a limiter so he wouldn't abuse it and overuse it, I'd only see him using it to protect Toki when he felt he had no other choice. And from what we've seen, he won't need it most of the time anyway.
Whether he uses it or not, this manga is still VERY unique among isekai manga. It starring an old martial artist isn't the only unique feature. The setting is totally different from what little we've seen of it, so far seeing more Asian influences than European. The character design and art style isn't the usual isekai art style, and we have yet to see any supernaturally beautiful people or royalty/nobility. Heck, I can't remember the last time I saw a race like dragon-newts. Dragons, sure, and dragons that transform into humans, but humans with dragon tails and fangs? Weirdly rare.
Best way I can describe it is that it's a shonen manga that's about isekai, rather than an isekai that's shonen, if that makes sense?