A menuga is someone that you share stories with that you don't tell everyone. A person that you feel very comfortable around, someone you hold no grudges against, and someone you really trust. However, there are boundaries both physical and mental that not everything in your life is open to your menugas. Introverts have a greater percentage of menugas as friends than extroverts.
How are menugas, friends, and acquaintances different you might ask? Acquaintances are people you know by name or reputation or their face but after maybe 30 seconds of talking there is an awkward silence. Friends are those people you spend time with and share stories with but you don't want them to see you cry and you don't tell them all of your exploits. Menugas are people you tell personal things to. They are people who have your best interests at heart. These people you share your failures with as well as your successes and they care about both.