How do you put an anime with 50+ episodes on a 25gb blu-ray disc

i have many anime movies at either 1080p/720p with 50+ episodes that i would like to put onto a blu-ray disc without losing the quality of the picture and keep the hard coded subtitles intact.
so, is there a program/s that can accomplish this task?

Did a bit of editing to forestall commentary on origin.

What is the total size of the videos now? If you have to compress them, you will inevitably lose some quality in this process. If it is done well, you may not notice it on playback.

Do you want a blu ray video, or are you just trying to back them up as data on a blu ray disc?

MultiAVCHD will be able to take multiple input files and build a new blu ray video for you. But if the videos you have now are not already compliant to blu ray specifications, they will be re-encoded to fit those requirements. And anime does better with a particular encoding profile in X264, that MultiAVCHD may not utilize.

So, examine the files with MediaInfo and see if they need to be re-encoded or not.

The other issue is the fact that MultiAVCHD is a picky beast, prone to crashing. But it is the only free program that will build your blu ray video with a menu so you can select each episode. There are commercial programs you could try instead.

i have multiavchd, tsmuxer, bd rebuilder, dvdnextcopy, handbrake, dvdfab, and etc.
i used multiavchd on the anime torrent with 50+ plus episodes but the quality of the of the anime turned out ok. i have seen 25gb blu-ray disc that had 50+ episodes on them with great quality just wished i knew how to do it.
i have GunGrave 1080p which about 14gb and want to put it on a 25gb blu-ray disc. when i use multiavchd it does the job but the hardcoded subs don’t show up when i play the disc.

Well, as I said, MultiAVCHD probably won’t use the best settings for anime. If the collection won’t fit onto a 25gb disc without compression, you might have to reduce their size by re-encoding with a program that will have very fine control of the X264 encoding parameters. Something like MeGUI. But this would only be for compression. MeGUI won’t author to blu ray video format.
A brief Google search should show you some entries for MeGUI X264 Anime guides.

I don’t work with anime at all, so I won’t be of much help.

If your GunGrave movie is already compliant to blu ray specifications, you can make a blu ray movie with no menu using a free program called Easy BD Lite. Hard coded subs should always show up though, so I’m not sure what is going on with your earlier attempt.