using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var text = "<span class=\"kanji-1-up kanji\">ま</span><span class=\"kanji-2-up kanji\">ちが</span><span></span>";
    	var textArray = Regex.Matches(text, @"(?s)<span(?:\s+[^>]*)?>(.*?)</span>")
    		.Cast<Match>()
    		.Select(x => x.Groups[1].Value);
        foreach (var item in textArray)
        	Console.WriteLine($"'{item}'");
	}
}

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