Many questions (e.g. 59726
67336 1455 59726) address the issue of how to change font attributes in section (and subsections etc). All of the ones I've seen end up requiring packages such as titlesec or sectsty, or suggest changing the document class to KOMA or something.
QUESTION: how to change the font attributes WITHOUT inserting additional packages nor changing the document class?
I ask this since I am using a specific document class called jlreq (a very good class for Japanese documents, specially if you need vertical writing) which conflicts with both packages abovementioned.
xpatch(non specialised in sections formatting) ;which enables to patch commands in any package or document class, in particular to replace the default font sizes with the ones you want. – Bernard Apr 24 '21 at 17:51jlreqdocument class, and a generic answer will not likely work. If you look at lines 5909 and following of the class, that's where the heading specifications are made using the class macro\NewBlockHeading. One of the keys supplied to the third argument of that macro isfont={...}with the font specification. Since the documentation is only in Japanese, I'm afraid I can't help you further. – Alan Munn Apr 24 '21 at 17:59