Quick answer
Use one Chiikawa in each row, column, and colour region; a first-puzzle checklist helps you test every placement.
The two puzzle traditions inform the stated constraints: use a Sudoku-style row and column check with a Minesweeper-style colour-region check before continuing.
For Chiidoku how to play, use the quick answer first, then check whether the topic affects a code reward, event, item, unit, map, build, value, or upgrade path.