I showed it to a native Japanese speaker and he thinks it's "Siera ga ookuri suru Thexder" though he said he was only able to make out "ga ookuri suru" part and

I showed it to a native Japanese speaker and he thinks it's "Siera ga ookuri suru Thexder" though he said he was only able to make out "ga ookuri suru" part and was inferring the rest from context. I feel like I can hear "Siera" at the start myself and you seemed sure the last word was Thexder, so that's what I'm going with. It's pretty nearly incomprehensible, though.