I have serious doubts about people who claim to regress to "littles". Seems a bit too cutesy for an actual disorder.

So- age regression can be a trauma response or something used in the context of therapeutic approaches to address past trauma (as in, with a therapist trained in the technique, although the use of this practice can be debated). People and more specifically kids with sometimes regress in response to big events (like their main care giver going back to work, moving houses, etc). The lay practice of engaging in this activity could have a wide array of rationale and implications. If this person is utilizing this as a coping technique at will (meaning there are choosing to engage in it) and not ‘stuck’ in this state regardless of environment or circumstance (meaning they would do it at work or in the grocery store, at home) then it could be that they are choosing times to engage in this activity.

People can essentially do what they want when they want (within the parameters of the law)- however, one could reasonably argue that when one chooses to engage in this behavior it should be so with regard to their environment and those around them. Others are not obligated to indulge the behavior (even if it is reportedly a coping behavior). Expecting others around you to completely understand and interact with the behavior is unacceptable unless otherwise, beforehand mutually agreed. (Additionally, there are other reasons to engage in this behavior which would not include coping, which could be in violation of someone else’s autonomy).

We are not islands and cannot reasonably expect others to understand and agree to engage with all behaviors we choose to utilize. Think about what if this person decided that screaming out for 5 seconds was something they liked or found useful. Okay. But they decide to do it in your living room, every 15 minutes. Would that not impact you? What if they went to the ICU and did the same behavior? It would not be okay and they would have to leave. Regardless of their personal rationale (even if it is possibly a trauma related behavior), it would not be acceptable to have them continue it in certain circumstances as it would impede on the needs of others.

In this situation, you were asking for clarity and information, they reacted. In a behavioral trend that is fairly individualized, understanding the nuances would require discussion. If someone wants you to participate in a behavior, it would be important that they discuss it with you. That being said, some questions can come across as blunt or otherwise- and should be asked before hand for clarity.

Finally, we do not have to condone or co-sign anyone’s behavioral choices- coping or otherwise. It is okay to say this doesn’t work for me. And it’s okay for them to say I don’t like you or I think you’re being this or that. It really all depends how much you care to get involved in this. It sounds like you like this person and because of that, you’re taking on this whole practice. But it doesn’t sound like you’re informed as to the ‘rules’ of it and therefore, leaves you little protection and understanding. So at this juncture, it would be super inappropriate to engage with it. Until and unless you not only are fully informed and agree, it should not be happening. This is fully a consent issue, full stop- regardless if it under the context of intimacy or sex or not.

You didn't mean to hurt their feelings. Write them a letter explaining everything