The synastry chart is a little hard to read, so not sure if I'm reading the aspects correctly.
It looks like a sun/mars opposition, which is a physical attraction. The Lilith on sun is very sexually compelling.
There is the Venus/mars trine and venus/mars opposition that kikaki mentions, that are both sexual ties, but the mars in the opposition is also conjunct Neptune/uranus.
Mars is the sexual and power drive in sexual affairs, but the Neptune is fantasy and avoidance, and in conjunction these two energies don't blend well. There has to be a strong lineup of other sexual attractions to counterbalance this contact. Mars has difficulty acting and expressing itself when it comes up against the Neptune nebulousness. So the sexuality tends to remain on a fantasy level.
There is a mutual mercury/vesta conjunction, so the idea of each of you seeing the other as a cosy, comfortable, domestic partner is there, but on an intellectual level.
This does seem to be more of a platonic friendship.
Looking at the composite to see how this all manifests in the relationship, there is Venus close to the sun, so this is an affectionate tie, and she is conjunct Lilith, so there is an attraction link. However, Venus has difficulty acting because she isn't integrated in the chart, aside from an inconjunct with Neptune, which brings us back to the idea of a dreamy contact that isn't concrete. The Venus/lilith conjunction is in an air sign, so more talking and communication than down to earth passion.
Mars is opposing the moon, again the feeling of sexual attraction, with a trine to feel-good Jupiter, but not a strong physical impulse, and not relating to Venus.
Can you do the charts with the inclusion of eros and psyche to see if they touch any of the planets? These are strong sexual asteroids. Also maybe amor, which is pure idealistic love.