Seiren

Seiren is a magic researcher in Rotsgard that supposedly dumped Raidou (Makoto) sensei and is now regretting her decision. She was the main focus of the "Atonement must be fast and plentiful" mini arc, and is now using Izumo as her assistant.

Appearance and personality
Not much is told of her appearance outside the fact that she is said to be a mature lady who always runs around in a white lab coat. When it comes to her personality, she has been shown to be a research otaku that pretty much only focuses on her research and things that can either support or advance her research anything else is seemingly irrelevant and because of it she appears extremely dense when it comes to anything outside her research.

Background
Seiren is at first one of the many nameless women that approaches Makoto when he first starts out as a teacher. They all approach him with the wish of him making them the number 2 or so on wife so that he would have to support them financially, but they wouldn't be expected to actually have anything to do with him. Being fed up with it and with Seiren being in his "strike zone" Makoto jokingly tells her that if she becomes his number 1 wife he will marry and support her. Seiren's respons is to look at him with disgust and run away while rejecting his proposal.

After this for some reason Seiren would go around and tell (brag?) everyone about how she rejected Makoto while it is never stated what her purpose for doing this ever was the result was that she became hated and ostracized by most of Rotsgard since Makoto had become the number one marriage target for all gold diggers and many others. Because of his action of saving Rotsgard, saint like personality, being super rich and so on with the only downside being his looks.

Relationships
Makoto Misumi: At first she only approached Makoto as a way to get funding for her research but after having him help her out with said research she realized that Makoto was actually the man of her dreams, because she's a research otaku, and he can perfectly read Aria's which is the base of her research. So she becomes deeply regretful of not accepting his proposal. (most people still seem to think Makoto was serious in his confession.)

Izumo Ikusabe: Izumo is forced by Makoto to hand over the knowledge he has gained after creating a new trump card called moving aria's to Seiren and eventually is semi-forced to become Seiren's assistant. Rumours have started to spread that they are in a relationship and Izumo is having an affair with a mature lady (Seiren) but far as we readers have been shown their relationship is purely professional.

Trivia

 * It has been mentioned in the mini-arc featuring Seiren that she together with Izumo will produce a great leap of knowledge when it comes to the research on Aria and it's applications.
 * Because of her being the only woman that Makoto had confessed to and shown interest towards while also being the only woman to have ever rejected him, she is at first seemingly the number one despised person of all the people related to Makoto in Rotsgard, especially among the women connected to Makoto who appeared to be quite jealous of Seiren while also being angry at her for rejecting Makoto.