MonaCoin is an internet meme based on a cat-like figure created using ASCII characters that was popularized on the community 2channel (rebranded as 5channel). It has been approved by Japan's Financial Services Agency and is accepted as payment in Japan.
According to Investopedia, MonaCoin has smaller trading volumes than Bitcoin and Ethereum. This partially due to its novelty, as well as its concentration in Japan. It is most frequently used through third-party mobile applications to provide tips, including in online games. The currency can be stored in and exchanged through Monappy. This is an online platform where MonaCoin holders can exchange coins for digital assets, such as coupons, electronics, and other items. The Monappy website also features online game streamers that accept MonaCoin as tips. MonaCoin can also be stored in third-party e-wallets.
Although there're different factors affect MonaCoin which would be considered to be a diversified portfolio, I don't think it is a wise choice to invest it in long term. The main reason is lack of information about the development team. People has no clue of what caused its chart climb up or down. According to cointobuy, the develop team have long since abandoned this project. As such there will be no further updates or support unless the community decides to take it over.