Dr. Maddie Ahn was Milo's elder sister. She was a leading expert in Android Production who created Nano in collaboration with MSA. Maddie was a brilliant researcher and the only one who succeeded incorporating the nanomachine manipulation program into an Android.
She has dark gray hair and pink eyes. She has been described as beautiful.
She was known to be confident, natural born genius, foulmouthed and displayed a lack of empathy towards others including Milo. However, she reflected on the devastation her creation was capable of and questioned her judgement after Milo was attacked by Chacha's Androids. She even eventually chose to sacrifice her own life to protect Milo and ensure that the Nano List technology was not compromised.