Alice in the Country of Hearts: My Fanatic Rabbit, Vol. 1

One day, a mysterious rabbit-eared man named Peter suddenly appears in
Alice's garden and kidnaps her, whisking her off to a dangerous world
where every resident brandishes a weapon. Trapped in this land in the
midst of a three-way power struggle, Alice accepts an offer to stay at
the Hatter's mansion. At the mansion, Alice meets the Hatter's
right-hand man, Elliot March, who is likable and charming and...also
sports a pair of bunny ears! And yet, Alice cannot get over the fact
that Elliot is actually a Mafia hitman, willing to kill people without
hesitation...In this popular Wonderland manga, the March Hare has finally
arrived!!