He has short brown hair and eyes, and seems to be slightly shorter than Natsume, Kitamoto and Tanuma. He is often seen wearing his school uniform, consisting of a white collar shirt and grey pants.
His other appearances is when he's out with his friends.
Nishimura is a funny and easy-going person with a slightly perverted sense of humour. Both he and Kitamoto went all out to be friends with Natsume, who wasn't willing at first. Eventually, they all become close friends.
He and Kitamoto befriended Natsume even when Natsume seemed reserved initially. Although he and Kitamoto noted that Natsume sometimes acted oddly,  they do their best to accept and support him as the series progresses.
They also taught Natsume how to ride a bicycle when they found out that Natsume did not know how. Together with Kitamoto, the three of them often plan activities to do during their free time.
Nishimura doesn't play a major role in the plot besides the fact that he is a close friend of Natsume. However, he isn't aware that Natsume can see youkai, unlike Tanuma and Taki.
In episode 69, he does play a major role. In the episode, he and Kitamoto both expect a female transfer student when they hear the news of someone transferring into their school. However, they both became disappointed upon realising that it was a boy, Natsume. Upon his first impression, Nishimura thought that Natsume seemed mature, quiet and reserved.
Their first conversation was when he had forgotten his pencil box (as he refers it) and was jogging back to his classroom. Upon discovering that Natsume is sleeping, he attempts to wake him up, only for Natsume to suddenly awaken and shout out "Stay away!" due to a nightmare. Nishimura begins laughing at Natsume whilst apologising, stating that he had never heard someone speak so clearly in their sleep. At this time, Natsume smiles and Nishimura realises that it was Natsume's real smile and that the smile he had shown around his other peers were fake. Upperclassmen soon reach the doorway and tell them to head home, Nishimura hurriedly takes Natsume's wrist and runs out of the classroom with him.
Their second encounter was when Natsume was attacked by a youkai. Nishimura had seen a shoe then decided to go to the bushes and saw Natsume seemingly unconscious. Natsume lies under the pretense that it was just anemia and Nishimura insists on allowing Natsume to visit his home so he can rest. Once they're at the Nishimura household, they make brief conversation about their families. During this time, Nishimura attempts to invite Natsume upstairs to his room on the second floor. Natsume politely refuses but briefly comments his room is on the second floor as well. Nishimura notes that Natsume seemed happy as he said that and proceeded to speak about his brother in which Natsume says he's envious.
During their conversation, Nishimura also notices that Natsume looked out their open door rather often. Soon, Natsume leaves during their conversation. The following day, he didn't come to school and Nishimura is grateful as he was uncertain as to how to approach him. Later, he speaks to Sasada and Kitamoto about how he really should've stayed at his home if he was feeling unwell. Sasada raises up the topic of Natsume continuously having to move from his relatives' homes and that he must've felt uncomfortable while he was with a stranger. Nishimura realises that speaking about his relationship with his brother must've been extremely inconsiderate.
Nishimura and Natsume often exchanged greetings only rather than hold proper conversations from then on. Kitamoto questions Nishimura to go and make up with Natsume if they had a fight and Nishimura replies stating that they weren't close enough to fight.
Soon after, Nishimura encounters Natsume reading a book about origami and how to fold paper cranes. He tells Nishimura that he's learning how to do so because someone Touko knew was in a hospital and wishes to fold 1,000 paper cranes. Nishimura snaps at Natsume (due to the influence of the youkai possessing him), stating how everyone knows how to fold paper cranes and that he should've asked them for help. He also comments rudely if the people around him seemed so unreliable that he wouldn't have asked them for assistance. While Nishimura is throwing his outburst, Natsume realises he's being possessed by a youkai.
After his outburst, realising how he had spoken, he slightly panics and bolts out of the bookstore and runs into a forest. As he runs, he feels like something big and black is riding his shoulders and how heavy his heart feels. When he reaches an empty point of the forest, he begins to realise that he needs to get out but doesn't know the way. He hears Natsume calling his name from a distance and it is shown briefly that Madara's binding light is present, most likely drawing out the youkai from Nishimura. While unconscious, he awakens for only a brief moment and can see the silhouettes of Madara and Natsume speaking to each other. Natsume states to Madara that he wanted to Nishimura was special to him because he was the first one that had spoken to him in the classroom and he was happy because of it. Proceeding to fall unconscious again, Nishimura thinks to himself that if it were the case, then Natsume should speak to him more rather than his cat.
Nishimura awakens in the hospital with Natsume coming to greet him. Soon after, they head to Nishimura's home and begin learning how to fold paper cranes. At one point, Nishimura becomes stumped, unable to recall the last steps, he suggests that at these times, they should see Kitamoto. However, Nishimura's brother appears and completes folding the paper crane after having taken it from Nishimura then leaves.
Natsume gazes enviously at them and comments how Nishimura's brother must've been kind. Nishimura says he doesn't know about that and wonders just how he had looked in Natsume's eyes during that moment.
- Main article: Nishimura's Brother
- Main article: Atsushi Kitamoto
- Main article: Takashi Natsume
- Main article: Kaname Tanuma
- Main article: Tooru Taki
He has a crush on Taki. This can be supported by the fact in which he had grabbed Kitamoto and Natsume so they could accompany him to her class. Although the feelings aren't mutual, Nishimura still persists at every opportunity, and often asks for Natsume's help to bring Taki along.  Also, Taki may not even be aware that Nishimura has a crush on her.
- Main article: Jun Sasada
- Prior to becoming friends with Natsume, he had been possessed by a youkai and began suffering from the symptoms. To name a few, he felt as though something was weighing down his heart, also feeling like something big and black had been riding on his shoulders and so forth.
- The youkai Nishimura had been possessed by is never shown besides being large and its hands about to creep over Nishimura while he was in the forest.
- The youkai most likely entered Nishimura's home while Natsume had been 'resting'. Natsume probably saw this, hence, his sudden departure.
- He knows how to fold cranes.
- He tends to get into fights with his mother over trivial things, for example, lunch.