Are you looking for strictly Japanese bread like what Esper posted, or are you just looking for the breads that they sell at Japanese convenience stores, including the Japanese-style apple danishes, cheese breads, etc?
In any case, since Esper covered the Japanese breads, here are some staple convenience store breads at almost all Japanese convenience stores (except Lawsons because Lawsons has to be the special butterfly and they end up with a crappy bread selection IMO. LOL)
Corn Filled Mayonnaise Bread (Super good, highly recommend) - You can find this in a bunch of other asian countries too.
Tuna Mayonnaise Bread - Same as above, but with tuna-- also amazing.
Okonomiyaki Bread - Admittedly never tried this since it's a bit heavy for breakfast, but it looks good?
Croquette Bread - 11/10 really amazing despite the fact that it's nothing but carbs
Yakisoba Bread - Literally just yakisoba in a hot dog bun.
Last I checked I only saw this Strawberry Twist being sold at Lawsons-- 0/10 I think it's gross and tastes like uncooked bread dough with strawberry jam in it. LOL
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Anyway, there's a ton more but if you don't mind the Japanese, here's a link to a blog that tries a ton of Japanese convenience store breads with pics and reviews:
https://konbinipan.com/
And here's another website that lists all the kinds of bread by convenience stores (7/11, Lawsons, Family Mart, Circle K, are the ones featured here. Where is the Sunkus love...)
https://コンビニパン.com/
I don't know if Japan's all that secretive about their stuff so much as it's just not very accessible unless you're searching in Japanese because nobody here speaks English worth a damn. But if you need any more information about anything, I can elaborate or help you figure out search queries. /thumbsup