Seijo Dakedo Yami Ochi Shitara Hiyoko ni Narimashita! @Comic

Betrayed by her comrades and killed, the former strongest saint of the human world is summoned to the demon world, only to find herself transformed into a tiny yellow "chick." Determined to repay the ruthless demon lord who bestowed upon her her fluffy form, she begins her second life—but her errands are reckless, leaving chick-shaped holes in doors, and her innocent training sessions result in overkill for the demon knights! Instead of living as a familiar, her baby-like mind only leads to disaster. And yet, the supposedly merciless demon lord blushes and declares himself her father!? "...I shall raise her (How adorable and brave. I must protect her!)" "Pi, pi, pi, pi, pi, pi, pi, pi!? (Oh, he's patting my head!?)" Everyone is inevitably melted by the chicks! A story of a runaway chick girl and her doting dad raising her child!

(Source: Comic Corona, translated)