Last Note has revealed (through an interview) that they are a two person unit, made up of Last Note (L-san,ラスノ) and Last Note T (T-san). Sadly, they will not be working together as Last Note anymore...
(According to Last Note's blog): s.ameblo.jp/lastnote25/entry-12061349591.html
(Partially) translation by Ame: amesubs.tumblr.com/post/126654822328/ame-san-could-you-please-translate-last-note-ts#notes
At least MSS will not be discontinued. It's a shame and really sad that they had to split, but I hope T-san does well.