Hermione's panties... :-S
Metalcore mixed with pop music is not a new thing - bands like Sonic Syndicate and Dead By April (I've had the gerat displeasure of experiencing the latter live) are known for their poppy approach to metalcore, and, frankly, it is not a type of metalcore that I particularly enjoy.
One Morning Left similarly combine metalcore and melodic pop, pairing harsh vocals and breakdowns with melodic clean vocal harmonies and dominant synths. Still, I think that One Morning Left's music is much more interesting with more stuff going on than the above mentioned artists. One Morning Left do not rely solely on power chords, but make use of actual riffage and guitar harmonies as well as guitar solos and lead melodies.
Granted, a lot of what they do sounds incredibly cheesy - especially, the use of the synths. However, song titles like '!liaF cipE', 'Hermione's Panties', and 'This Song Has a Massive Autotune Chorus' along with the use of extremely cheesy electronica elements as well as incredibly funny things, like over-the-top pig squealing in 'Reetu inda House' and 'Hey Yo. Let's Play Tycoon' seem to suggest that One Morning After take the piss out of the entire metalcore genre.
In essence, "The Bree-TeenZ" is a spoof album, which parodies the metalcore genre while observing its conventions (and that is, of course, the best kind of spoof). What is more - whether you like the music or not - One Morning Left definitely are good musicians and, while they seem to be making fun of metalcore-pop, they still make better music, I think, than most other metalcore-pop acts I have heard.
If this is a spoof/parody album, which seem to be the case, then it is well nigh a stroke of genius. If it isn't, then it is a !liaF cipE. In any case, it will evoke some laughs.