The fifth doll of the dolls, and The Protagonist of the series. She is restrained, noble and sometimes demanding, but is nevertheless a good-hearted doll who simply does what she feels needs to be done.
Basically the other main character of the series, being the guy who actually kicks off the plot by winding up Shinku. In short, he is a reclusive loser who has a fear of school after failing on a test and becoming the laughing stock of his class.
Break the Cutie: Practically the reason he became a Hikikomori, specifically he was dismissed by his peers becaused he likes sewing, and his self-image went downhill from there.
Book Dumb: Just before he shunned schooling altogether. Justified as he is already too broken at this point.
Ordinary High School Student: Subverted in that he doesn't exactly go to school. He does start going to school in the manga, and is studying to catch up everything he lost before going back in the anime.
Tsundere: Type A. She is usually Tsuntsun on other people and her sisters, but Deredere to Megu.
Villainous BSOD: In the manga, after learning that Hinaichigo willingly gave her Roza Mystica to Shinku, she realizes that Souseiseki's Roza Mystica had been hurting her because she stole it. She lets both Suiseiseki and Souseiseki go because of this to reflect upon the purpose of the Alice game, commenting snarkily that she will take demand the Roza Mystica back later rather than at that point.
The second Rozen Maiden doll, Kanaria makes her appearance only later in the series. Her medium is named Mitsu (but everyone calls her Micchan), who is a maniac doll collector and her artificial spirit is names Pizzicato. Kanaria considers herself to be the smartest Maiden and often boasts about it, but her plans almost always fail in hilarious ways. Personality-wise, she is similar to Hinaichigo and like her and Suiseiseki, Kanaria have a Verbal Tic: "Kashira" (Feminine version of "I wonder?" adaptated to "Maybe" in the official english release of the manga). However, Kanaria is competent in battle and battle using sonic waves of her violin.
Badass Boast: She tries to do one in the manga, but Older!Jun interrupts it much to her dismay.
The Chew Toy: Kanaria, who screws up every time without anyone noticing.
Crouching Moron, Hidden Badass: While she is similar to Hinaichigo personality-wise, she is very competent in battle, managing to defeat Suiseiseki, Souseiseki, and Hinaichigo simultaneously in the anime. Also in the manga it's stated that she protected Jun from Kirakishou while he was hiding from her in the N-Field and also managed to destroy Kirakishou's illusions using the sound of her violin.
Too Dumb to Live: Although she claims to be the smartest Rozen Maiden doll, none of her plans seem to work. To round off the Too Dumb to Live, she tried fighting four Rozen Maidens at once. Also, on the final episode of the anime, when Barasuishou destroys her violin, she stands still, not realizing she can use Suiseiseki's power.
The Heart: She's the first one to try and convince the other dolls that the whole Alice Game is a worthless endeavour.
Heroic Sacrifice: In the anime, she tries to take on Barasuishou herself to give Kanaria a chance to escape. Sadly, this turns into a Senseless Sacrifice when Kanaria decides to keep on fighting. They both end up dead because of it. The manga has another one, more successful one in which she sacrifices her own roza mystica to revive Souseiseki fully and banish Kirakishou from her body. She gets better in both of these cases, however...
Imagine Spot: In a recent manga chapter, she has one of those after reading a shoujo manga... so we get to see Suiseiseki wearing a school uniform recieving a love confession from a boy (who strangely looks like Jun).
The McCoy: She refuses to fight the Alice Game because she cares too much about her sisters.
Being the fourth doll of the Rozen Maidens, Souseiseki is the most duty-bound of the dolls, and the most restrained. She feels that she is obliged to become Alice, mostly out of a sense of duty. She is commonly the most calm and collected of the dolls, and is strongly bound by her sense of honor and duty.
Emotionless Girl: Played straight towards the other dolls, then subverted when she dies in the hands of Enju.
The drama CDs revealed that not only does she rarely show any emotion, she is practically unable to, as when Enju and Shirosaki make her seem more alive and upbeat in personality, she still sounds just as emotionless as a Genki Girl, Tsundere, and bondage queen as she usually does.
Evil Knockoff: She was created by Enju for the simple reason to prove that Enju was a superior doll-maker.
Freudian Excuse: Unlike the other dolls, she was created with no physical body, and was thereby forced to live out her life alone in the N-field, eventually driving her insane out of an intense wish to gain a physical body and a lack of social experience with other dolls and humans.