1. Introduction

青空文庫記法 (Aozora Bunko notation) is the annotation language used to mark up the plain-text works of Aozora Bunko, Japan's volunteer digital library. It encodes the typographic features of printed Japanese books — ruby (furigana), emphasis dots and side lines, out-of- repertoire glyphs (gaiji), classical-Chinese reading marks (kunten), indentation and alignment, page and section breaks — as inline directives inside otherwise ordinary text, e.g.

　明治の頃｜青梅《おうめ》街道沿いに、可哀想［＃「可哀想」に傍点］な話。

This document specifies that language normatively: precisely enough that two independent implementations, reading only this text, produce the same result for the same input.

1.1 Scope

This specification defines:

the character-level input a conforming processor accepts, and the normalization applied before parsing (§3, §4);
the lexical grammar of notation constructs (§5, Annex D);
the notation catalogue — every directive and inline construct, its parameters, and its meaning (§6);
the structural processing model — pairing, nesting, and forward-reference resolution (§7);
a reference rendering to HTML and a byte-exact serialization round-trip (§8);
the diagnostics a processor reports for malformed input (§9); and
conformance, anchored by a machine-readable test-vector suite (§10).

It does not define a file format, a transport, a stylesheet, or the visual appearance of any construct beyond a reference mapping.

1.2 Relationship to the official 注記一覧

The authoritative human-facing description of the notation is Aozora Bunko's official 注記一覧 (annotation guide), https://www.aozora.gr.jp/annotation/. That guide is the source of record for intent: which constructs exist and what they mean. It is, however, prose-and-example only — it has no formal grammar, no precise processing model, and no conformance suite, and in several places it is silent or ambiguous about edge cases.

This specification follows the official guide wherever it is determinate. Where the guide is silent or admits more than one reading, this document makes an explicit normative decision, grounded additionally in the forms and frequencies actually observed in the Aozora Bunko corpus. Each such decision is recorded as a decision record (referenced from the relevant section) so that the choice — and its rationale — is auditable rather than folkloric.

This specification is independent and is not endorsed by or affiliated with Aozora Bunko.

1.3 Document status

Status: draft v0.1.0

The framework (§§1–5, 7–12) and the notation families in §6 are normative. A few families that the official guide itself treats as provisional — 太字 / 斜体 (§6.12), 表 / 段組 (§6.13), saidoku-moji (§6.5), and some layout directives (§6.6) — are documented with their notation, but their full normative semantics are deferred to a later revision and not yet required for conformance; each is flagged where it appears (see §10.5).

1.4 Conformance levels (overview)

Normative requirements use the keywords of §2. Conformance is verified against the test vectors of §10, each tagged must, should, or may. A conforming processor matches every must-level expectation; the lower levels scale the obligation down. The full contract is in §10 and in conformance/RUNNER.md at the repository root.

1.5 Document conventions

Japanese notation strings, keywords, and examples are given verbatim in Japanese; surrounding explanation is in English. Full-width punctuation that is significant to the grammar (［＃］《》｜ ※ 「」（）〔〕) is shown as-is and identified by Unicode scalar value in Annex D. Byte offsets in examples and vectors are UTF-8 byte offsets into the sanitized source (§4).