Edgelord magic-school manga incoming!
And for all those worried -- this has no relation to "The Irregular at Magic High School" (Mahouka Koukou no Rettousei), which more directly translates as "Bad student of the Magic Department of Senior High". This title more directly translates to "Worst person of the Royal Magic Academy".
"Rettousei" means "poor student" and more directly refers to ability, while "saika-sei" ought to be "worst person", ie "scum", and implies something about morals or social standing.
Not sure why both have chosen "irregular" as the translation, that ought to be hiseiki (非正規) I think, as in "irregular army". My Japanese is pretty terrible though and completely colored by samurai period dramas and yakuza movies-- so don't take my word for it.