Do not play Sunrider Academy first! You will ruin the series as it a fan service game with those characters.
You will go in with expectations of the characters and will be disappointed.
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Sunrider's Dev says (In that link): Mask of Arcadius -> Liberation Day and then Sunrider Academy is a spin off school years for some of the cast (alternative universe). It should also be noted that save importing will only work for your save from MoA and into LD.
Personally I would do: Mask of Arcadius -> Sunrider Academy -> Liberation Day.
It is a lot easier to appreciate the references if you play MoA first and there are foreshadow moments in Academy to the events of LD (as Academy was released between MoA and LD).
Ultimately you just need to make sure you have played MoA before going into LD, Academy can technically be played without playing either.