Responding to someone who tells you "I really want you" depends on your feelings and the context of the conversation. Here are some possible responses, ranging from direct to more nuanced, depending on your comfort level and intentions:
Direct response: a. If you feel the same way: "I feel the same way about you." b. If you don't feel the same way: "I appreciate your honesty, but I don't share the same feelings."
Gentle refusal: a. "I value our friendship (or relationship), but I don't see us being more than friends (or whatever your current relationship status is)." b. "I think you're a wonderful person, but I'm not looking for a romantic relationship right now."
Needing time to think: a. "Thank you for sharing your feelings with me. I need some time to process this." b. "I didn't expect this, and I need to think about it before responding."
Clarification: a. "When you say you want me, can you explain what you mean exactly?"
Remember that it's important to be honest and respectful in your response. If you're not interested in pursuing a romantic relationship with the person, be considerate of their feelings. Similarly, if you are interested, communicate your feelings clearly. It's essential to be open and authentic in your response, while also being mindful of the other person's emotions.