Between October 2016 to June 2018, a solo album was produced introducing a new Girl of the Month. Each EP contained 2-3 songs, sung by the titular girl.

Love&Live was released on March 13, 2017, with title song Love&Live. The Theme of this era was the theme of love as the members express the innocence and excitement of having a first crush. Later, on April 27, 2017, it was repackaged and released as Love&Evil.

Mix & Match was released on September 21, 2017, with title song Girl Front. The theme of this era was a girl crush concept around the theme of love and attraction. The members are portrayed as being playful and tempting while expressing their fondness and seduction towards their beloved ones. Other subjects in their songs include playfulness, temptation, romance and intimacy. Later, on October 31, 2017, it was repackaged and released as Max & Match, Loona's first studio album.

Beauty & the Beat was released on May 30, 2018, with title song Love4Eva (ft. Grimes). The theme of this era was the love of youth so shiny to seem luminous. They decide to be truthful to their emotions in the moment, free of worries about what may come tomorrow. There was no repackaged album for this EP.

[+ +] was released on August 20, 2018, with title song Hi High. Its description reads "LOOΠΔ was born in its own universe with three uniquely structured teams. In other words, it was not designed as a group diving up into three units, but three teams were built to create one universe."

[XX] was released on February 19, 2019, with title song Butterfly, as a repackaged version of [+ +]. [XX] was their first studio album as an entire group. Its description reads "While [+ +] portrayed a basic addition of each other, [X X] is an applied multiplication of each other."

[#] was released on February 5 2020, with title song So What. # was their first EP without HaSeul. Its description reads " If [+ +] was about the basic combination of adding each other, [X X] was about the applied combination of multiplying each other.
Just like how # has little meaning when used by itself, but manifests in special functions or great achievement when used alongside words and characters, [#] is about how we can realize results from multi-use combinations when we are together."

[12:00] was released on October 19, 2020, with title song Why Not?. Its description reads "LOONA discovered destiny in between coincidence and fate. After creating unimaginable waves of change through [#], LOONA realize that their destiny is the role of pioneer for all LOONAs around the world, and decide to follow their inevitable reason for existence. LOONA, predicting that a new moon will rise, decide to hold a festival in the concert of moonlight at [12:00], when the Moon radiates the brightest light before it expires, one where not even a single girl is oppressed. Having created coincidence by colliding fate against fate, and discovered destiny between coincidence and fate, LOONA delivers a new message through the midnight festival. With all LOOΠΔs around the world; like this slogan of the album, that message says that all LOONAs of the world are always together, that all are dignified and equal, worthy to earn freedom. The combined voice of the girls, who face the beginning of a new moon, is cast into the world."