I myself open ~always at tengen if i get to be black on 9x9, mostly because that tends to turn into big fight early on, thus preventing white getting relatively easy “komiwin” by splitting the board into two about equally sized territories.
There is this principle for even 9x9 games: "white should aim at making two small living groups or make a big territory worth of 15 points. Either way, black shouldn’t normally be able to build up enough points to win against komi, so black should aim at preventing white from doing those things
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Oh yeah, if you’re interested, there is a collection for 200 most common openings on 9x9 and what answer has had the highest winrate at GoQuest You can thank Ootakamoku for creating it ^^ https://www.suomigo.net/wiki/Fuseki9x9