NuType · font licences

Fira Mono (weights 500, 700)
Copyright (c) 2012-2013, The Mozilla Corporation and Telefonica S.A.
SIL Open Font License 1.1: /licenses/fira-mono-OFL.txt
Served unmodified.

Yuji Syuku (weight 400)
Copyright 2021 The Yuji Project Authors (https://github.com/Kinutafontfactory/Yuji)
SIL Open Font License 1.1: /licenses/yuji-syuku-OFL.txt
Served as a subset of the original glyphs for ニュータイプ, a Modified Version under the licence.

Helvetica is the reader's own system font; no file is served for it.