While watching the anime, I thought that "The Dangers in My Heart" is a boy's perfect fantasy. Now that I'm reading the manga (up to Karte 100 at the moment), I starting to think that it is
also a girl's perfect fantasy.
Let's start with Ichikawa's superficial qualities, that Yamada likes or at least might like. Ichikawa is academically successful, and teachers are praising him for further improvements. Yamada doesn't mind his fashion sense (see the scene when they discuss that he dresses in all black); the extra manga chapters with flash-forwards even show that Yamada started to match her jewelry to Ichikawa's skulls on his clothes. She also seems to be attracted to his body, as seen in the scene when they compare his right arm just out of the cast to his left arm.
Ichikawa helps and protects her in difficult situations. The very first encounter in the library where he lent her his box-cutter knife is an example. Then he distracted the Pickup-senpai with his bicycle. Ichikawa also helped with rehearsing for her first film. Later, their late night talk about him being worried that he isn't a good son helped her with her role as well.
Most importantly, Ichikawa understands Yamada on a level, which even Kobayashi and her other friends don't. This is mostly shown through scenes, where Ichikawa discusses Yamada's work and her feelings about it with her. Ichikawa also understands very well what worries Yamada. Aside from instances, when Ichikawa is overwhelmed by his insecurities, he has an incredible ability to say just the right thing to Yamada.
Another positive quality of Ichikawa is that he gets along pretty well with Yamada's friends, her parents (!), and his sister.
Unlike Kanzaki and Adachi, Ichikawa is never rude or vulgar. Unlike Pickup-senpai, Ichikawa got to know Yamada before the confession.
P.S. I reposted this on reddit, where there's some discussion and interesting points made by commenters: