https://ideone.com/ND1ToN

KemonoLang.cs

using System;

public class Test
{
	const string PINC  = "たのしー！";
	const string PDEC  = "たーのしー！";
	const string INC   = "すごーい！";
	const string DEC   = "すっごーい！";
	const string PUT   = "なにこれなにこれ！";
	const string GET   = "おもしろーい！";
	const string START = "うわー！";
	const string END   = "おもしろーい！";
	
	/*
	const string PINC  = ">";
	const string PDEC  = "<";
	const string INC   = "+";
	const string DEC   = "-";
	const string PUT   = ".";
	const string GET   = ",";
	const string START = "[";
	const string END   = "]";
	*/
		
	public static void Main()
	{
		Print("Friends");
	}
	
	private static int Put(char c, int cur = 0)
	{
		var diff = c - cur;
			
		var ope  = (diff > 0) ? INC : DEC;
		var sqrt = (int)Math.Sqrt(Math.Abs(diff));
		var x = sqrt + 1;
		var y = sqrt;
		var offset = diff - x * y;
		
		if (offset < 0) { offset += y; x--; }
		
		// optimize
		for (var i = 1; i < x - 1; ++i)
		{
			var tmp = diff - (sqrt + i) * (sqrt + i);
			if (0 <= tmp && tmp < offset)
			{
				x = sqrt + i;
				y = sqrt - i;
				offset = tmp;
			}
		}
		
		if (diff < (x + y + 3))
		{
			Console.Write(PINC);
			for (var i = 0; i < Math.Abs(diff); ++i)
				Console.Write(ope);
			Console.Write(PUT);
			Console.Write(PDEC);
			return c;
		}
		
		// set a repeat number
		for (var i = 0; i < x; ++i)
			Console.Write(INC);
			
		// loop start
		Console.Write(START);
			
		Console.Write(PINC);
		for (var i = 0; i < y; ++i)
			Console.Write(ope);
		
		// loop decriment
		Console.Write(PDEC);
		Console.Write(DEC);
		
		// loop end
		Console.Write(END);
		
		Console.Write(PINC);
		for (var i = 0; i < offset; ++i)
			Console.Write(ope);
		
		// output
		Console.Write(PUT);
		
		Console.Write(PDEC);
		
		return c;
	}
	
	private static int Print(string str, int cur = 0)
	{
		foreach (var c in str)
			cur = Put(c, cur);
		return cur;
	}
}