Swapping roles is the whole point of the game
When your two cats alternate, one sprinting down the hall after the other and then, minutes later, being chased back the other way, they are rehearsing a hunt sequence together and agreeing, turn by turn, to keep it friendly. A cat who has just been chased and then chooses to chase is telling you the pursuit felt safe. Healthy chase play also stops and starts, with pauses for a wash, a drink or a look out of the window, and both cats return to shared spaces afterwards instead of one vanishing for hours.
The body language that keeps play play
Watch bodies, not noise. In play, ears point forward, tails are up or loosely level, and the chasing cat often runs in an exaggerated, bouncy arc rather than a low, fixed line. There may be soft wrestling with sheathed claws and inhibited bites, followed by both cats shaking off and relaxing nearby. Vocal noise alone does not settle it either way, since some cats chirp and trill through play while others are silent even when annoyed. The swap itself, plus loose muscles and easy breaks, is your most reliable evidence.
Where reciprocal play tips into bullying
Bullying is one-sided in three ways at once: the same cat is always the one fleeing, the encounters happen around resources rather than in open space, and the target's daily life shrinks. A bullied cat starts waiting until the other is asleep to use the litter tray, eats quickly while glancing up, gives up favourite sleeping spots, or hides under a bed after each chase. Look for small scabs or thinning fur around the head, neck and base of the tail, and for staring contests where one cat blocks a doorway and will not break eye contact.
What to change at home before you separate them
Give the fleeing cat geography first: a tall cat tree with two levels, shelves or a cleared bookcase top, and at least two routes out of every room so she is never cornered at a single doorway. Feed the cats in separate spots with a door or baby gate between them at first, and keep litter trays in more than one quiet location. Then drain the pursuer separately with a vigorous wand session before the times of day when ambushes usually start, often early evening, so his urge to chase something is already partly spent.
When to get outside help
If one cat is losing weight, toileting outside the tray, hiding for most of the day or carrying repeated small wounds, book a vet visit for the target cat first, because pain and illness can make a cat both more likely to be picked on and less able to cope. If both cats are medically clear and the one-sided pattern continues for several weeks despite extra routes, resources and separate play, a qualified feline behaviourist can visit and read the layout and the pair's history together. Do not punish the chasing cat, since that adds stress without teaching him another outlet.
Spending the bold cat's energy on a schedule
The separate play sessions only protect your quieter cat if they happen on the evenings you are tired or out, too. KinsLe Care Teams lets you assign that pre-evening wand session for the bolder cat to different household members on different days, with each completed session timestamped, so the cat who needs the outlet most is not relying on one person's memory.