Sexual Misconduct involving Breast (Women)?

Here is a traditional view of sexual misconduct as I understand it.

The Daśākuśala-karma-patha-nirdeśa (Explanation of the ten virtuous paths of action) authored by Aśvaghoṣa. While the breasts are not explicitly mentioned, he says:

What are inappropriate body parts?
The mouth, the anus, the calves or
Thighs pressed together, and the hand* in motion

*(this includes one's own hand).

So, while the breasts are not mentioned, we can safely conclude that using the breasts in a manner similar to the thighs or calves pressed together is inappropriate: This is because the list is not an exclusive list - Aśvaghoṣa does not say 'the inappropriate'.

Much of the following comes from the same and correlating texts:

Sexual misconduct may appear complex, but really it can also be seen to be quite simple.

If we recognise that the function of sex is procreation rather than recreation then - first of all, any form of sex that is not procreative is misconduct, even with eligible partners.

Secondly, any form of procreative sex with an unsuitable partner is likewise misconduct.

If you and your partner are both consenting, both free from any ties of family or other people, of fertile (legal) age, married to each other or both unmarried, belong to different families, are not bound by vows or decisions of celibacy, engage in a private place where any cries of passion will not be heard, during the hours of darkness, and only at those times of the month where conception is likely; and if both of you and your families are all willing to accept the consequences and responsibilities of raising a child together into adulthood if a pregnancy were to occur, knowing that nobody will object to your choice of partnership, then this is not sexual misconduct - unless your sex is on a holy day, close to a holy site, monastery, temple, and so on, in which case it is misconduct. (Likewise, to have more than five o*g**ms in a night is excessive, and is sexual misconduct).

So this is pretty restrictive. The Dalai Lama offered an alternative, suggesting that maybe monks don’t understand married life so well.

In this, it allows for recreational sex, as long as there is no harm done to anybody and if there is explicit consent freely given by involved parties. ‘Harm’ also includes STDs, lack of disclosure, and anything leading to a furtive behaviour, emotional hurt of either the involved or uninvolved parties. He has spoken of this on a few occasions.

However, and regardless, full responsibility by all parties for unintended consequences (children) is required always - and this means being present in their lives and actively raising them - not merely paying child support. He has talked on this many times.

Always consider the possible consequences before doing anything.

In the Pali canon, sensual (or sexual) misconduct as one of the five precepts is defined as:

He misconducts himself in sensual pleasures; he has intercourse with women who are protected by their mother, father, mother and father, brother, sister, or relatives, who have a husband, who are protected by law, and even with those who are garlanded in token of betrothal.
MN 41

So for lay persons, it is more about adultery, infidelity, and a sensual relationship outside of a committed exclusive relationship (or marriage) with a free consenting adult (of legal age), rather than a specific sexual practice or fetish.

So, what's bad about sexual misconduct? What is the consequence that is to be avoided?

The minimum result it (sexual misconduct) leads to for a human being is rivalry and enmity.
AN 8.40

And what is the purpose of virtue?

"Skillful virtues have freedom from remorse as their purpose, Ananda, and freedom from remorse as their reward."
AN 11.1

Remorse typically comes from harming others in a way that you would not like to be done to you (Ud 5.1).

I don't see any cause for rivalry, enmity or remorse from the practice of "unnatural" sex within a committed exclusive relationship (or marriage) with a free consenting adult.

So, does that mean that specific sexual practices and fetishes are acceptable within a committed exclusive relationship (or marriage) with a free consenting adult?

It's definitely forbidden for monks, nuns, novice monks, novice nuns, anagarikas and those temporarily observing uposatha (stricter practice).

For lay persons outside this scope, it is not forbidden by the minimum prescribed training (i.e. the five precepts). However, serious practitioners may very well consider restraining their extreme desires.

In Buddhism, lust for sex is treated just like greed or lust for other sensual pleasures. Sexual addiction is no more evil than gluttony.

"Now suppose that there was a leper covered with sores & infections, devoured by worms, picking the scabs off the openings of his wounds with his nails, cauterizing his body over a pit of glowing embers. The more he cauterized his body over the pit of glowing embers, the more disgusting, foul-smelling, & putrid the openings of his wounds would become, and yet he would feel a modicum of enjoyment & satisfaction because of the itchiness of his wounds. In the same way, beings not free from passion for sensual pleasures — devoured by sensual craving, burning with sensual fever — indulge in sensual pleasures. The more they indulge in sensual pleasures, the more their sensual craving increases and the more they burn with sensual fever, and yet they feel a modicum of enjoyment & satisfaction dependent on the five strings of sensuality.
MN 75

-- Officer, I was only going a little over the speed limit

To understand misconduct, we need to understand the reason for the rules we adopt. The rules are guides on our journey to letting go of suffering. The rules protect us against certain dangers. What dangers should we beware?

The Buddha warns against relishing. If we wish to stop suffering, we need to deal with relishing:

MN1:172-194.26: Because he has understood that relishing is the root of suffering,

Relishing is built on craving. If we wish to stop suffering we should understand craving:

AN6.106:1.2: What three cravings should you give up?
AN6.106:1.3: Craving for sensual pleasures, craving for continued existence, and craving to end existence.

Sensual pleasures are hard to let go of. They are the itch that gets worse if we scratch them and torment us if we try to ignore them. Screaming at us in the back of our minds is the thought, "I have an itch I need to get rid of now".

The first thing we learn on the path is that Identity is a view. This "I am" is a view. And because identity is simply a view, we can choose another view. We can choose to think, "here is an itchy feeling". This view opens up new possibilities. And one of those new possibilities is that we might watch the itchy feeling just as we might watch our breaths coming in and out.

Watching feelings is part of mindfulness meditation. And as we train ourselves in mindfulness meditation, we start noticing something quite peculiar. Feelings cease. Feelings arise and feelings cease all on their own.

Sometimes feelings are useful to us. Feeling uneasy in a burning building, we would seek to escape. And that would be a good escape from fire.

But what about sexual feelings? Sexual feelings can feel powerful and urgent, just like the urge to flee a burning building. But what if, what if sexual feelings ARE the fire seeking to burn the house? Sexual feelings can make people do very strange things. Goaded by sexual feelings we might hurt others. Goaded by sexual feelings, we might use others as objects, demanding, trading and selling them at a whim. Clearly we need to set boundaries to such madness.

The rules help us set boundaries to our misconduct. They limit suffering for ourselves as well as others. The rules give us time to let go of obsessions that bring suffering. And that time to let go is very important, because it gives us a chance to take a deep breath and look around us, to see what matters and let go of things that don't matter.

When we ask "is this misconduct?", we are really asking for permission to do something we doubt will bring us lasting happiness. We are thinking, "if only I had a little bit of this, then I could be a little happier." And yet we also find that chasing that little bit of happiness just brings a little bit of suffering, endlessly. We become old people chasing young feelings.

The odd thing about meditation is that meditation also brings us happiness. And the happiness brought by meditation stretches out to the point where sensual pleasures stop screaming at us. But meditation takes time.

If we haven't meditated enough, sensual feelings will still plague us. And we need some way to deal with them. In particular, we need to expand our awareness in each moment. To do so, we have to think about others. And here the rules again help us:

MN8:12.39: ‘Others will be conscienceless, but here we will have a sense of conscience.’
MN8:12.40: ‘Others will be imprudent, but here we will be prudent.’

So, instead of thinking about sexual objects such as breasts, it is better to understand that we are interacting with people. Breasts are attached to people. Have we even thought about what other people care?

Breasts are not the danger here. Flaming desire is the danger here. Flaming desire blinds and torments.