Why does その辺 mean “regular”?

Question

寿季「だって、なんというか……ずっと憧れの人だったわけで……」

桐葉「あら、そうなの？」

寿季「月見坂さんは俺のこと、その辺のファンだなぐらいに思っていただろうけど……」

寿季「俺は君が心の支えだった。そのぐらいまで月見坂ーー月見桐奈のことが好きだったから」

寿季「多分……このことが無かったら、俺は月見坂さんに告白していたと思うぐらいには」

桐葉「……そうなんだ。ちょっと照れちゃうわね」

Context: A girl called 月見坂桐葉 offers to become 寿季’s girlfriend. The girl is his schoolmate and is admired by 寿季.

I asked what this その辺 means elsewhere and a native speaker told me it meant “regular” in this context. I don’t know why it means that even if I know it originally means “thereabouts”. Or do you think it means something else there? Please shed some light on it.

If the context is insufficient, please let me know.

Answer 1

その辺 literally means 'around there'. The implication is that you do not have to look too far, you can find 'it' anywhere so that it means 'regular' figuratively.

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Note that その辺 can be used non-figuratively, literally referring to some particular area. E.g. その辺で買った can mean I bought it around there (there understood by context) or The shop I bought it is fairly ordinary (implying such a shop can be found anywhere).