Throughout the course of the game Shiki meets new friends and talks about old friends. There are some that stick out to me more than normal and I feel them to be extremely important to Shiki's growth as a person. I will go on to explain who they are and why.
The first person of importance is Eri, Shiki's best friend. Not much is known about her at first, but what little bit of information that slips through her lips early on, and the picture we see on her cell phone, indicates a deep admiration for her. The two met one day when Eri saw her working on what turned out to be Mr. Mew. Realizing Shiki had a sharp eye for sewing the two of them became fast friends and an essential part of each other; Eri was the one who would design the clothes while Shiki was the one who would sew them together. As Eri put it Shiki brought everything she made to life and made them real. Something she claimed she herself was unable to do.
Their friendship was shattered one day, however, when Eri had told Shiki that she wasn't meant to be a designer, in an attempt to cheer her up, when she was frustrated that anything she designed didn't turn out well. Eri had meant that Shiki had a really good future as a seamstress but realized that what she had meant to say came out wrong and wanted to apologize. Unfortunately Shiki died in an accident before she was able to. Eri claims she will always regret what she said and had even considered quitting designing because she feels incomplete without Shiki. Even in death Eri still considers Shiki her best friend. When Shiki learns of this she becomes even more determined to win the Game so that she and Eri can become the team they were once again.
The second is Neku Sakuraba, her partner in the Game. Neku comes off as a bit of a hot head and a jerk toward Shiki early on––even going so far as to call her a stalker––and states that he is only using Shiki as a means to survive the Game. The guy's missing his memory though so I guess it is to be expected. He ignores Shiki the majority of the time and also claims to be better off alone and that people only drag him down. However, as the week progresses he becomes less resistant toward Shiki and even takes the time to listen to what she has to say. He even openly admits to her that he can't remember anything but his name.
When Shiki and Neku are confronted by the Game Master Shiki goes into a funk and loses all will to win the Game. When he learns the truth about Shiki, that the way she looks is not her real appearance, he is nothing but supportive of Shiki. When Shiki claims she will still be the same old Shiki that she hates, and nothing like Eri, he states that she is Shiki and will never be Eri. He even admits to liking Shiki the way she is. At the end of the week Neku even starts calling Shiki by her name instead of "hey you" like he had been all week, and promises to meet at the statue of Hachiko, the place where they first met, when they come back to life. When Neku is forced to re-enter the Game Shiki becomes his new entry fee, and makes it his goal to win for her sake.