Follow the Leader: So, as this is the second adaptation of the dark and mystical novel by P.A.WORKS studio, the RDG inherits many artistic decisions and atmosphere of their Another adaptation.
Ending Aversion: many viewers were dissatisfied with almost sudden transformation Izumiko in the last series of the show, which only complicated the general involvement of the plot.
Incest Subtext: Relationship between Souda triplets may well be regarded as quite normal for twins caring for each other, however, some viewers found heavy subtext in their relationship due to a combination of their Half-Identical Twins nature and rather ambiguous image of twin's communication in last part of the series. This is especially true moments where Mayura wants to "give Manatsu her heart and be with him one whole" or when Manatsu seems repeatedly annoyed when he heard about the idea find a fiancé for his sister.
In the last few episodes subtext almost become text when Mayura tries to avoid marriage in order to stay together with her brothers, and her conversation with Manatsu in the last series looks like a his refusal to respond to her feelings
Ho Yay: Based on the context described above, Manatsu's words that his brother fall in love with someone other except him and their sister, sound quite ambiguous.
Periphery Demographic: Although the original story was conceived as a Shoujo and have a number of similar trope like innocent main heroines with tsundere-boy love interest, adaptation positioned as a series for teenagers of either sex and, accordingly, received a similar audience.
The Scrappy: Izumiko. Her weak personality was one of the things that threw some viewers away.