Unified Legal AI Agent 'Legal Brain Agent' Achieves 'Top-Tier Passing Level*1' in Japan's Most Difficult 'Preliminary Bar Examination (Essay Questions) ‘

  Bengo4.com, Inc. (Minato-ku, Tokyo; Taichiro Motoe, Representative Director, President and CEO, Lawyer; hereinafter, “the Company”) is pleased to announce that its unified legal AI agent, 'Legal Brain Agent,' scored 375 out of 500 points*2 on the essay portion of the 2025 Preliminary Bar Examination. 
  This answer was evaluated as 'Top-Tier Passing Level*1' based on grading by Hogakukan Co., Ltd., which operates 'Ito Juku,' a leading bar examination preparatory school that also leads the industry in the number of successful candidates. 
  Furthermore, when compared with major general-purpose AI models, it outperformed them in all 10 subjects. 

*1: The evaluation of 'Top-Tier Passing Level' is an opinion based on Hogakukan Co., Ltd.'s many years of teaching experience and unique grading criteria in response to the score of 375 points achieved in this grading. 
It does not indicate official grades or rankings published by the Ministry of Justice. 
*2: The grading criteria for this examination are not public, and official scores are calculated after adjustments for grading disparities across all examinees. 



◾️Overview 
  Preliminary Bar Examination is an examination to obtain eligibility to take the Bar Examination without attending law school. 
  While the pass rate for the Bar Examination itself is typically around 40-45%, the pass rate for the preliminary test remains around 3-4%, making it an extremely difficult national examination. 
The final pass rate for the essay-style examination of the 2025 Preliminary Bar Examination was 3.6%*3. 
  Among these, the "essay-style examination," which consists of 10 subjects, requires advanced logical thinking. 
  Therefore, grading the answers requires professional judgment, making it difficult to objectively evaluate the capabilities of AI. 
  To objectively visualize the essay-writing ability of the "Legal Brain Agent," we requested grading from an external specialized institution, Hogakukan Co., Ltd., and it received an evaluation of "top-tier passing level*1." 
  This is the first case*4 in Japan where an AI has been evaluated as reaching a passing level for the essay-style examination of the Preliminary Bar Examination after being graded by an external specialized institution. 
*3: Calculated from the Ministry of Justice's "Results of the 2025 Preliminary Bar Examination." 
*4: First in Japan as a published case evaluated as reaching a passing level after grading by an external institution in an "essay-style" examination (as of June 2026, based on our research). 

■ Outperforms General-Purpose AI Models Across All 10 Subjects, Achieving "Excellent" in 5 Subjects and Zero "Poor" Ratings 
  Under identical questions and conditions, answers generated by major general-purpose AI models were also graded simultaneously. The results demonstrated that the "Legal Brain Agent" successfully outperformed the general-purpose AI models across all 10 subjects. 
  Furthermore, when applied to the official grading criteria published by the Ministry of Justice (classification of qualitative evaluation of answers), the "Legal Brain Agent" received the highest rating of "Excellent" in 5 out of 10 subjects, and the lowest rating of "Poor" in 0 subjects. 
  When general-purpose AI models were graded using the same criteria, they achieved "Excellent" in only 0 to 1 subject. 


■ Background
Adapting to Essay Structuring and Legal Reasoning, in Addition to High-Precision Information Retrieval 
  The ability of the "Legal Brain Agent" to handle the highly advanced essay section is driven by the following factors.
  Proprietary Knowledge Database: Generates answers based on "Legal Graph," a proprietary legal information infrastructure that structures the relationships between laws, judicial precedents, and specialized legal books

Continuous Quality Improvement by Lawyers
  A dedicated team composed of practicing lawyers continuously verifies the accuracy and comprehensiveness of the points in the answers. 
  By identifying specific types of problems—such as "misinterpretation of intent" or "inaccurate information"—and utilizing our proprietary legal reasoning algorithms, the team drives a continuous feedback loop from root cause analysis to correction and testing. 

Unified Legal AI Agent
  An AI agent that supports a wide range of tasks, from organizing consultation content and brainstorming to research and document creation. It understands the context of the dialogue and accompanies legal work while grasping points and risks. 

◾️Verification Method 
The overview of this verification is as follows. 
・Test Scope: 2025 Preliminary Bar Examination Essay Section, 10 subjects in total / Max. 4 pages each (Elective:Insolvency Law ) 
・Response method: Inputting the question text into the Legal Brain Agent and two major general-purpose AI models, respectively, and instructing them to output answers. 
・Grader: Hogakukan Co., Ltd. (Ito Juku) 
・Data handling: The reference database for the 'Legal Brain Agent' does not include model answers for this examination or examinees' reproduced answers. 

◾️Future Outlook 
  This essay-type verification is the second accuracy verification following the 2025 Bar Examination 'Short-answer type' examination, where it recorded a 96.5% correct answer rate (169 out of 175 points), surpassing the highest score of the examinees. 
  These results demonstrate that it has become capable of the thinking process required in essay-type examinations: 'accurately referencing legal provisions and precedents, applying them to facts, and deriving logical conclusions,' rather than just the ability to solve problems. 
  Based on the insights gained from these two verifications, the Company will continue to further improve AI accuracy and expand content such as legal books and case law data. 
  We will support all processes of search, analysis, and judgment in legal practice more quickly and accurately, and promote the realization of a 'society where everyone can access reliable legal knowledge' through the evolution of AI technology. 

◾️Comment from Hogakukan Co., Ltd. (Ito Juku) 
'These results have made me realize once again the evolution of the 'Legal Brain Agent'. 
Although a simple comparison cannot be made because the grading criteria and examination conditions differ from the actual examination, I believe it is a noteworthy achievement that AI achieved these results in the Preliminary Bar Examination (essay questions).
Legal professionals who master high-performance AI like this 'Legal Brain Agent' will likely be able to demonstrate their advanced expertise and judgment more than ever before. 
However, to maximize the power of AI, unwavering basic legal knowledge and logical thinking skills are essential. 
For us as well, this was an opportunity to reaffirm the necessity of supporting examinees who aim to become professional legal experts in a new era, so that they can build that 'solid foundation'. 

◾️Comment from Maki Kadonaga, Attorney at Law, Partner and Chief Knowledge Officer,  Anderson Mori & Tomotsune 
'The fact that such high performance has been demonstrated in the core of legal practice—logical structuring based on facts—beyond mere knowledge search, clearly shows the essential potential of legal AI. 
I strongly expect that Legal Brain will evolve into a platform that further enhances the quality and efficiency of legal practice while highly integrating with the expertise of legal professionals, and will realize further technological innovation and the expansion of social implementation.' 

■Comment from Yuji Inagaki, Head of Product, LegalBrain Business Division, Bengo4.com, Inc.
“I am very grateful for this valuable opportunity, made possible through the cooperation of Ito Juku. 
Legal Brain Agent was developed with the concept of 'Supporting legal professionals with AI,' with the utmost focus on the accuracy of its responses. 
In the highly specialized field of legal affairs, generative AI is prone to certain errors, and we have received many comments from professionals expressing concern about the possibility of mistakes being mixed into the output. 
Legal Brain Agent is designed to generate responses based on reliable legal databases and to enhance accuracy by clearly indicating the grounds for its answers, aiming to provide a tool that professionals can use with peace of mind. 
We will continue to strive to expand its features and improve its accuracy so that it can become an even more reliable tool for lawyers and In-house legal departments. 

■ About Legal Brain Agent

   Legal Brain Agent is a unified legal AI agent designed for lawyers and in-house legal professionals, powered by Legal Brain, a proprietary legal AI technology infrastructure developed by Bengo4.com. Its fundamental differentiator from general-purpose AI lies in its design philosophy: it bases its responses solely on highly reliable sources—such as Japanese laws, regulations, precedents, guidelines and specialized legal books, and articles from "BUSINESS LAWYERS"—and ensures that every answer is accompanied by citations and references to the original sources.
Service Website: https://legalbrain.com/