Pluto in the 5th house synastry means their Pluto falls in your 5th house: where their intensity lands in your life. What it feels like from both sides, the gift, the shadow, and how to find your overlays.
Pluto in the 5th house synastry means their Pluto falls in your fifth house: romance, flirtation, play, creative work, children, the part of you that wants to be adored. Their intensity lands on your joy. The attraction tends to be immediate and a little too strong, the kind that makes a casual date feel like a decision.
Their Pluto in your 5th house
This is one of the classic obsessive-attraction overlays, and it usually announces itself. For you, the romance feels bigger than the circumstances: the flirting is charged, the sex, if it gets there, is memorable, and being wanted this hard is flattering up until it is exhausting. Your creative work may take a turn under their gaze, darker or braver. If children are involved, they take a serious interest in yours or in the question of having them. For them, you are the person they cannot stop thinking about, and the desire to be your one and only can arrive before the first date is over. They tend to watch who else makes you laugh. Pluto's sign belongs to their whole age group; landing in your fifth house is what makes them fixate on your light.
The gift
Being wanted without reservation, and finding out what that does to you, is the upside. Playing, flirting and making things with them tends to pull work out of you that you did not know you had in you: the song you finally finish, the risk you take on stage. Pleasure gets serious in a good way. Your delight is the thing they are protecting, and when they manage to enjoy you without gripping, they learn what lightness feels like.
The shadow
Jealousy is the failure mode. A friend's hand on your arm becomes an argument, an evening out without them becomes a negotiation, and your creative life can start to feel like it needs their approval before it counts. You may dim your own sparkle to keep the peace, which defeats the point of a fifth house. They may treat your attention as something they are owed. Possessiveness is not proof of love; it is a habit to name and stop, on either side.
Working with it
Keep making things that are not about them. Book the class, the gig, the night with friends, and go, then notice whether the fallout is a mood or a punishment; the difference matters. Let them adore you and say when it tips into monitoring, in the moment, not later. If there are children, agree together where their influence stops. Flirt with each other on purpose so the intensity has somewhere joyful to go.