You could take one look at the "shoujo" tag on this manga and see it coming from a mile away. Nearly everything that's here seems painfully familiar, and I'm not that well-acquainted with the genre as a whole.
Much like a sushi sampler, Mizuto-san offers up a standard assortment of shoujo heroines in a standard set of high school situations: the first story focuses on a strong-willed transfer student who follows her heart when her morals are challenged; the second tale offers a look at a girl harboring a decade long crush on a boy who showed her kindness; and the final yarn recounts the trials of a young lady who comes in contact with the god of a cherry-tree shrine. None of these girls break their unoriginal molds to any degree. Every platitude, inner monologue, and declaration can be found in a far superior manga executed to with more skill.
Much like the derivative plot, Mizuno's art brings nothing new to the genre, but doesn't offend the eyes. The mangaka executes her boys-with-flowers portions acceptably serving up a cast of tasty bishies that the reader can easily tell apart, but falls down almost everywhere else. Her shoddy sense of blocking in particular needs work, as it mutates a dramatic kiss in the first story into a confusing mishmash of panels.
With no time to delve into these characters, Mizuno boils them down to their most basic elements. The boys are heroic, caring, or disaffected as suits their particular story and the girls do little more serve as vessels for their love of their fated partners. The protagonist of the longest tale, Tohri, starts with a backbone and some character traits, but quickly sheds herself of them once she falls for her romantic interest. Given that the heroines drive shoujo romance, these insipid characters prove a massive disappointment.
Sure, the omake chapters are amusing, but on the whole this manga feels like a bag of those candied valentine hearts: sweet, but not tasty and very bad for you. While the prevalence of interminable shoujo titles makes a one-shot appealing reading it only vindicates the decision of superior mangaka to tell longer tales.