"You're right. I can struggle until I cough up blood, and people will still die. Cruelly and mercilessly, without even a shred of ideals... that is how the world works. But even if the path I seek is a parched desert of thirst and suffering, I will continue to seek my ideals!"
Kunikida is a tall and slim young man with dirty blonde hair and deep, green-grey eyes. His bangs are parted to the right and he has rather neat, but spiky hair that ends in a long ponytail. He is always seen wearing his glasses.
His attire consists of a beige vest over a black long-sleeved dress shirt, a red ribbon tied into a bow around the collar, beige pants, and plain brown shoes.
As a member of the Armed Detective Agency, Kunikida is very professional and diligent when it comes to his job because to him, the reputation of the agency takes precedence over anything else. He constantly feels the need to organize, gather, and schedule every bit of detail, which is why he may come off as somewhat too strict and harsh during investigations.
He can also be seen as practical to a fault, as he almost considered abandoning a kidnapped Atsushi because the boy's presence might implicate the agency. Despite this, Kunikida is nonetheless a trustworthy and loyal detective that many in the agency rely on because of his authoritative capability and responsible nature.
He is almost never seen without his trademark notebook, which he believes to be an "ideal" and guide to life. He utilizes its function for several reasons, such as data-gathering, planning, making the world a better place, and most importantly, a medium for his ability, Doppo Poet.
While depicting a calm and careful front, Kunikida is also known for his exasperated outbursts, which is primarily caused by his partner, Osamu Dazai, who constantly vex him with his suicidal attempts. However, Kunikida does not genuinely dislike Dazai. He especially acknowledges Dazai's skill and knowledge when first working with him, and continues to entrust much of the Agency's strategies to Dazai. Similar faith extends to Ranpo Edogawa, as Kunikida actively participates in letting Ranpo believe Ultra Deduction is a real ability, reverent of Ranpo's detective prowess and its value to the Agency.
He is also uncharacteristically naive and is prone to easily believe Dazai's lies, which he later jots down in his notebook for future reference.
Kunikida values human lives, as he strives to save all innocent people during dangerous events in Yokohama. He sticks to this belief after seeing incidents of youth injured or killed in front of him. As a result, Kunikida never thinks of killing his opponents as the only option, constantly to right wrongs without the need for bloodshed. Due to his dedicated compassion to try to protect the city and its people, Ranpo believes he is the strongest and most virtuous person in the agency.
This calm front begins to crack when he is forced to "bend the rules", resulting in a mental breakdown.  Kunikida's mental state continues to deteriorate when being hunted by the Hunting Dogs, losing self-confidence and "the light he always sees on the other side of the mirror".  His ideals are challenged by Saigiku Jōno, who calls them "big and lofty as a hot air balloon". He believes that Kunikida's ideals will disappear if his comrades die and he will feel "relief".
Kunikida deeply thinks about this statement, causing him to re-evaluate his ideals drastically, saying that "idealistic thought alone won't save lives, it's time to be more realistic". By the end of the chapter, Kunikida makes a self-sacrificial decision, sticking to his desire to keep his comrades alive and telling Tetchō Suehiro that he "won't let anyone ruin his plans" and "with this life as fuel, he will fly for eternity".
Kunikida's ability, The Matchless Poet (独歩吟客 Doppo Ginkaku?, literally "Lone Poet"), allows Kunikida to make objects written on the papers of his notebook come into existence. However, it does not work on objects larger than the notebook. Such objects include wire guns, handguns, grenades, and flashbangs.
He is shown to be able to use pre-written notes as a means for his object summons, which can be especially convenient if one of his hands is bound and incapacitated. Also, he is able to remotely activate his ability, transforming pre-written notes into objects, which come in handy when supporting other members from afar. 
Nevertheless, his ability possesses a great flaw, since the pages of his notebook are limited, and getting a new one is expensive.
- "Just what is an 'ideal'? [...] If you ask me, the answer is clear. It is a word written on the cover of my notebook. My notebook is omnipotent. It guides me as a principle, as a master, as a prophet. At times, it becomes a weapon and also a key."
- (to Aya Koda) "My ideal world is not one where people die before my eyes. Such are my thoughts."
- (to Tetchō Suehiro) "My name is Doppo Kunikida! I will not let my ideals fall! With this life as fuel, I will fly for eternity!"
- Kunikida, along with several other characters, appeared in the mobile game Love Heaven as a limited-time character.
- His conditions for an ideal partner total to 58.
- According to Kafka Asagiri's tweet, Kunikida was a college drop out.
- BONES incorporates the events with Nobuko Sasaki into the anime, involving Atsushi in them. This contradicts the canon timeline of events.
- Kunikida once worked on a side job twice a week by teaching algebra at the New Tsuruya Academy, which mirrors the real-life Doppo Kunikida who taught mathematics, along with English and history, at the Tsuruya Academy sometime in 1893.