Ooooh, more Kamen Rider references:
https://dynasty-scans.com/chapters/after_school_re_reincarnation_ch10#5
That card gun is VERY similar to KR Diend's Diendriver from KR Decade. Also the Spirit Golem is clearly inspired by old-school mecha anime (and more modern revivals of that like SSSS.Gridman which this specifically reminds me of).
Huh. I figured that was supposed to be a Yu-Gi-Oh reference.
Cards are how the Riders in Decade (aired in 2009) transform and also activate their powers. Tsukasa Kadoya, the main rider uses a belt called "Decadriver", and Daiki Kaito, the secondary Rider uses a gun-shaped tool named "Diendriver". By loading cards collected from other Riders, both can utilize their powers, which for Diend includes summoning monsters.
Another KR series involving a card motif is Kamen Rider Blade (aired 2004) and it also features a gun with cards, the Garren Rouzer used by Kamen Rider Garren, but since the function here is closer to the Diendriver's, I think this is what sometime was referencing.